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Neurological diseases of viral origin in cattle in the state of Pernambuco, Brazil: clinical and anatomopathological study

Abstract

Studies related to neurological diseases are of great importance in Veterinary Medicine, particularly those involving production animals, such as cattle, due to their wide sanitary and public health significance. Therefore, the current study aims to describe the frequency of occurrence of the main clinical, laboratory, and anatomopathological findings of cattle diagnosed with neurological diseases of viral origin. Screening was performed in the general register of patients diagnosed through anatomopathological and/or complementary examination with illnesses of viral origin, admitted (live or dead) to the Clínica de Bovinos de Garanhuns-UFRPE from January 2009 to December 2019. The information recovered was entered in a database created in the computer program Microsoft Excel 2010®, distributed into clinical, laboratory, and anatomopathological data. The clinical findings on neurological diseases of viral etiology were very varied and non-specific, and the anatomopathological findings, together with laboratory methods, were of fundamental importance for the establishment of the diagnosis. The high frequency of rabies cases in this study demonstrates the importance of this disease for cattle rearing, as well as for Public Health. We emphasize the importance of including malignant catarrhal fever and herpes meningoencephalitis in the differential diagnosis of neurological diseases in the region, as well as the adoption of sanitary measures.

Keywords:
clinical findings; rabies; herpes meningoencephalitis; malignant bluetongue; anatomopathological findings

Resumo

Os estudos relacionados as doenças neurológicas assumem grande importância na Medicina Veterinária, particularmente os que envolvem animais de produção como os bovinos, em virtude da grande importância sanitária e de saúde pública. Nesse contexto, este trabalho teve como objetivo descrever a frequência de ocorrência dos principais achados clínicos, laboratoriais e anatomopatológicos dos bovinos diagnosticados com doenças neurológicas de origem viral. Realizou-se a triagem no livro de registro geral dos pacientes com enfermidades que cursaram com sintomatologia neurológica e que foram diagnosticados através de exame anatomopatológico e/ou complementares com enfermidades de origem viral, os quais deram entrada (vivos ou mortos) na Clínica de Bovinos de Garanhuns-UFRPE no período de janeiro de 2009 a dezembro de 2019. As informações obtidas foram inseridas em um banco de dados elaborado no programa de computador Microsoft Excel 2010® distribuídas em dados clínicos, laboratoriais e anatomopatológicos. Os achados clínicos das enfermidades neurológicas de etiologia viral foram muito variados e inespecíficos, sendo os achados anatomopatológicos, aliados aos métodos laboratoriais, de importância fundamental para o estabelecimento do diagnóstico. A elevada frequência dos casos de raiva neste estudo demonstra a importância sanitária desta enfermidade para a pecuária bovina, como também para a saúde pública. Ressalta-se a importância da inclusão da febre catarral maligna e da meningoencefalite herpética no diagnóstico diferencial das doenças neurológicas na região, assim como a adoção de medidas sanitárias.

Palavras-chave
achados clínicos; raiva; meningoencefalite herpética; febre catarral maligna; achados anatomopatológicos

1. Introduction

Studies related to neurological diseases are of great importance in Veterinary Medicine, particularly those involving production animals, such as cattle, due to their great sanitary and public health importance (11 Wuthrich D, Boujon CL, Truchet L, Selimovic-Hamza S, Oevermann A, Bouzalas IG, Bruggmann R, Seuberlich T. Exploring the virome of cattle with non-suppurative encephalitis of unknown etiology by metagenomics. Virology. 2016;493:22-30. (https://doi.org/10.1016/j.virol.2016.03.009).
https://doi.org/10.1016/j.virol.2016.03....
,22 Hierweger MM, Werder S, Seuberlich T. Parainfluenza Virus 5 Infection in Neurological Disease and Encephalitis of Cattle. International Journal of Molecular Sciences. 2020;21(2): 1-19. (doi: 10.3390/ijms21020498).
https://doi.org/10.3390/ijms21020498)...
). The emergence of bovine spongiform encephalopathy, in the mid-1980s, and its subsequent association with the variant of human Creutzfeldt-Jakob disease (vCJD), highlighted the socioeconomic and health importance of central nervous system diseases in this species, and the need for improvement in differential diagnosis (33 Barros CSL, Driemeier D, Dutra IS, Lemos RAA. Doenças do sistema nervoso de bovinos no Brasil. Coleção Vallée, São Paulo, 2006. 207p.). Neurological diseases are responsible for significant economic losses in Brazilian livestock, showing great relevance in the agricultural scenario due to the frequency with which they occur, often in the form of outbreaks, in many cases presenting low morbidity, but with high lethality rates in affected animals (33 Barros CSL, Driemeier D, Dutra IS, Lemos RAA. Doenças do sistema nervoso de bovinos no Brasil. Coleção Vallée, São Paulo, 2006. 207p.,44 Sanches AWD, Langohr IM, Stigger AL, Barros CSL. Doenças do sistema nervoso central em bovinos no sul do Brasil. Pesquisa Veterinária Brasileira. 2000;20(3):113-118. (https://doi.org/10.1590/S0100-736X2000000300005).
https://doi.org/10.1590/S0100-736X200000...
,55 Ribas NLKS, Carvalho RI, Santos AC, Valençoela RA, Gouveia AF, Castro MB, Mori AE, Lemos RAA. Doenças do sistema nervoso de bovinos no Mato Grosso do Sul: 1082 casos. Pesquisa Veterinária Brasileira. 2013;33(10):1183-1194. (https://doi.org/10.1590/S0100-736X2013001000003).
https://doi.org/10.1590/S0100-736X201300...
).

In recent years, retrospective studies of the diseases that affect the nervous system of cattle have been carried out in different regions of the country, however, despite the importance of the diagnosis, a significant portion of the cases remain unclear, lacking an etiological diagnosis, representing a constant concern for human and animal health (66 Theil D, Fatzer R, Schiller I, Caplazi P, Zurbriggen A, Vandevelde M. Neuropathological and aetiological studies of sporadic non-suppurative meningoencephalomyelitis of cattle. The Veterinary Record. 1998;143(9):244-249. (https://doi.org/10.1136/vr.143.9.244).
https://doi.org/10.1136/vr.143.9.244...
,77 Sánchez M, Clark EG, Wobeser GA, Janzen ED, Philibert HA. A retrospective study of non-suppurative encephalitis in beef cattle from Western Canada, Canadian Veterinary Journal. 2013;54(12):1127-1132. Disponível em: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3831384/pdf/cvj_12_1127.pdf.
https://www.ncbi.nlm.nih.gov/pmc/article...
). Infections of viral origin assume significant importance, particularly, in greater prominence, those associated with the rabies virus and bovine herpesvirus type 5 (BoHV-5) (44 Sanches AWD, Langohr IM, Stigger AL, Barros CSL. Doenças do sistema nervoso central em bovinos no sul do Brasil. Pesquisa Veterinária Brasileira. 2000;20(3):113-118. (https://doi.org/10.1590/S0100-736X2000000300005).
https://doi.org/10.1590/S0100-736X200000...
,55 Ribas NLKS, Carvalho RI, Santos AC, Valençoela RA, Gouveia AF, Castro MB, Mori AE, Lemos RAA. Doenças do sistema nervoso de bovinos no Mato Grosso do Sul: 1082 casos. Pesquisa Veterinária Brasileira. 2013;33(10):1183-1194. (https://doi.org/10.1590/S0100-736X2013001000003).
https://doi.org/10.1590/S0100-736X201300...
,88 Riet-Correa F, Schild AL, Fernandes CG. Enfermidades do sistema nervoso dos ruminantes no Sul do Rio Grande do Sul. Ciência Rural. 1998;28(2):341-348. (https://doi.org/10.1590/S0103-84781998000200028).
https://doi.org/10.1590/S0103-8478199800...
,99 Reis MC, Costa JN, Peixoto APC, Figueiredo LJC, Menezes, R. V.; Ferreira, M. M.; Sá, J. E. U. Aspectos clínicos e epidemiológicos da raiva bovina apresentados na casuística da Clínica de Bovinos (Oliveira dos Campinhos, Santo Amaro, Bahia), Universidade Federal da Bahia, durante o período de janeiro de 1990 a dezembro de 1999. Revista Brasileira Saúde Produção Animal [Internet]. 2003;4(1):12-17. Disponível em: https://academic.naver.com/article.naver?doc_id=437684339.
https://academic.naver.com/article.naver...
,1010 Lemos RAA, Rech RR, Guimarães EB, Kadri A, Dutra IS. Febre catarral maligna em bovinos do Mato Grosso de Sul e de São Paulo. Ciência Rural. 2005;35(4):932-934. (https://doi.org/10.1590/S0103-84782005000400030).
https://doi.org/10.1590/S0103-8478200500...
,1111 Lima EF, Riet-Correa F, Castro RS, Gomes AAB, Lima FS. Sinais clínicos, distribuição das lesões no sistema nervoso e epidemiologia da raiva em herbívoros na região Nordeste do Brasil. Pesquisa Veterinária Brasileira. 2005;25(4):250-264. (https://doi.org/10.1590/S0100-736X2005000400011).
https://doi.org/10.1590/S0100-736X200500...
,1212 Barros, C.S.L. Neuropatias Bovinas Emergentes. Ciência Animal Brasileira, [S. l.], v. 1, 2009. Disponível em: https://www.revistas.ufg.br/vet/article/view/7667. Acesso em: 14 jan. 2022.
https://www.revistas.ufg.br/vet/article/...
,1313 Galiza GJN, Silva MLCR, Dantas AFM, Simões SVD, Riet-Correa F. Doenças do sistema nervoso de bovinos no semiárido nordestino. Pesquisa Veterinária Brasileira [Internet]. 2010;30(3):267-276. Disponível em: https://www.scielo.br/j/pvb/a/Sp7yJkQgTJ55XLpBqp7JdzH/?lang=pt&format=pdf.
https://www.scielo.br/j/pvb/a/Sp7yJkQgTJ...
,1414 Terra JP, Blume GR, Rabelo RE, Medeiros JT, Rocha CGN, Chagas IN, Aguiar MDS, Sant’ana FJFD. Neurological diseases of cattle in the state of Goiás, Brazil (2010-2017). Pesquisa Veterinária Brasileira. 2018;38(9):1752-1760. (https://doi.org/10.1590/1678-5150-PVB-5768).
https://doi.org/10.1590/1678-5150-PVB-57...
,1515 Queiroz GR, Oliveira RAM, Flaiban KKMC, Di Santis GW, Bracarense APFRL, Headley SA, Alfieri AA, Lisbôa JAN. Diagnóstico diferencial das doenças neurológicas dos bovinos no estado do Paraná. Pesquisa Veterinária Brasileira. 2018;38(7):1264-1277. (https://doi.org/10.1590/1678-5150-PVB-5429).
https://doi.org/10.1590/1678-5150-PVB-54...
). Rabies is the most relevant central nervous system disease in cattle in Brazil (1616 Borges AS, Lisbôa, J.N, Braga PRC, Leite, RO, Queiroz GR. Doenças Neurológicas Dos Ruminantes No Brasil: Exame E Diagnóstico Diferencial. Revista Brasileira de Buiatria - Clínica Médica, Volume 1, Número 3, p. 63-99. 2021.). In the country, the annual loss of cattle due to rabies is estimated at approximately 17 million dollars or approximately 850,000 head (1111 Lima EF, Riet-Correa F, Castro RS, Gomes AAB, Lima FS. Sinais clínicos, distribuição das lesões no sistema nervoso e epidemiologia da raiva em herbívoros na região Nordeste do Brasil. Pesquisa Veterinária Brasileira. 2005;25(4):250-264. (https://doi.org/10.1590/S0100-736X2005000400011).
https://doi.org/10.1590/S0100-736X200500...
). It is estimated that bovine rabies in Latin America causes annual losses of hundreds of millions of dollars, caused by the death of thousands of head, in addition to the indirect expenses that may occur with the vaccination of millions of cattle and countless post-exposure treatments of people who had contact with animals with a suspected infection (1717 BRASIL. MINISTÉRIO DA AGRICULTURA, PECUÁRIA E ABASTECIMENTO. Controle da raiva dos herbívoros: manual técnico 2009 / Ministério da Agricultura, Pecuária e Abastecimento. Secretaria de Defesa Agropecuária. - Brasília: Mapa/ACS, 2009.124p.).

The expansion of information regarding these diseases, as well as other viruses that involve the nervous system of cattle, is of great value for the adoption of measures aimed at the health of the cattle herd. The objective of this study was to describe the frequency of occurrence of the main clinical, laboratory, and anatomopathological findings in cattle diagnosed with neurological diseases of viral origin.

2. Materials and methods

The study was performed at the Clínica de Bovinos de Garanhuns-UFRPE. Initially, screening was carried out in the general record book of patients diagnosed with illnesses that presented with neurological symptoms, diagnosed through anatomopathological and/or complementary exams with illnesses of viral origin, and admitted (alive or dead) to the institution in the period from January 2009 to December 2019. Subsequently, clinical records and post-mortem examination records were accessed. The information obtained was entered in a database prepared in the Microsoft Excel 2010® computer program distributed into clinical, laboratory, and anatomopathological data.

As a routine clinical procedure, the animals underwent a clinical examination at the time of hospital discharge, in accordance with the guidelines by Dirksen et al. (1818 Dirksen G, Gründer HD, Stöber M. Rosenberger: Exame clínico dos Bovinos. 3.ed. Rio de Janeiro: Guanabara Koogan; 1993. 419p.). Hematological exams (hemogram and determination of total protein and fibrinogen plasmatic concentration) were performed as described by Harvey (1919 Harvey J W. Hematology procedures. In: Harvey JW. Veterinary hematology. A diagnostic guide and color atlas. St. Louis: Elsevier; 2012. 368p.). The animals that died were submitted to anatomopathological exams (2020 King JM, Roth-Johnson L, Dodd DC, Newsom ME. The Necropsy Book: A guide for veterinary students, residents, clinicians, pathologists, and biological researchers. 7 ed. Ithaca: Cornell University. 2013. 259p.).

As these are neurological diseases, therapeutic intervention was instituted when there was a possibility of disease regression and clinical indication. According to the evolution and severity of the clinical signs, the animals were clinically monitored, as long as they did not reach situations of terminal suffering, when euthanasia was indicated (2121 Conselho Federal de Medicina Veterinária. Guia Brasileiro de Boas Práticas em Eutanásia em Animais - Conceitos e Procedimentos Recomendados. Conselho Federal de Medicina Veterinária, Brasília-DF, 2013. Disponível em: https://www.cfmv.gov.br/guia-brasileiro-de-boas-praticas-para-a-eutanasia-em-animais/comunicacao/publicacoes/#1. Portuguese.
https://www.cfmv.gov.br/guia-brasileiro-...
). Tissue fragments of organs from the thoracic and abdominal cavities, central nervous system, lymph nodes, and skin were collected, fixed in 10% buffered formalin, and histopathological examination was performed (2222 Luna L G. Manual of histologic staining methods of the Armed Forces Institute of Pathology. 3 ed. New York: McGraw-Hill Book; 1968. 258p.), using Hematoxylin and Eosin stain (HE).

All animals submitted to necropsy that presented neurological manifestations were tested for rabies. Fragments of the brain (cortex and hippocampus), cerebellum, and spinal cord were sent frozen to the Agricultural Defense and Inspection Agency of the State of Pernambuco (Adagro) for direct immunofluorescence (DIF) and biological testing in mice (2323 Dean DJ, Abelseth MK, Atanasiu P. Fluorescent Antibody Test. In: Meslin, F.X.; Kaplan, M.M.; Koprowski, H. Laboratory Techniques in Rabies. 4 ed. World Health Organization, Geneva; 1996. p.88-95.). Confirmation of the diagnosis of meningoencephalitis due to BoHV-5 or BoHV-1 was based on the suggestive results of the histopathological examination and confirmation of the presence of viral DNA in the nervous system by means of the polymerase chain reaction (PCR) (2424 Claus MP, Alfieri AF, Médici KC, Lunardi M, Alfieri AA. Bovine herpesvirus 5 detection by virus isolation in cell culture and multiplex-pcr in central nervous system from cattle with neurological disease in brazilian herds. Brazilian Journal of Microbiology. 2007;38(3):485-490. (https://doi.org/10.1590/S1517-83822007000300019).
https://doi.org/10.1590/S1517-8382200700...
). Both samples preserved in paraffin and frozen were submitted to PCR, as described by Silva (2525 Silva, B.P. Identificação e caracterização molecular do Bovine alphaherpesvirus 1 e Bovine alphaherpesvirus 5 em bovinos no estado de Pernambuco. 2021. 121p. Tese de Doutorado. Universidade Federal Rural de Pernambuco. Recife, 2021.). The diagnosis of malignant bluetongue was based on clinical epidemiological and anatomopathological findings. For data analysis, a descriptive statistical model was used, observing the distribution of variables through relative and absolute frequencies for each disease (2626 Thrusfield M. Epidemiologia Veterinária. 3.ed. São Paulo: Roca, 2005. 610p.).

3. Results and discussion

During the eleven-year period studied, a total of 6,103 cattle were treated, of which 604 (10.1%) were diagnosed with neurological diseases. Of these 604, 21.5% (n=130) had a viral etiology, with 101 (77.7%) cases of rabies, 19 (14.6%) cases of malignant bluetongue, and 10 (7.7%) cases of herpes meningoencephalitis.

3.1 Rabies

Affected cattle had a predominantly paralytic clinical picture, related to spinal cord, brainstem, and cerebellum injuries, together with signs associated with brain injuries (Table 1). These findings have also been reported by other authors. (99 Reis MC, Costa JN, Peixoto APC, Figueiredo LJC, Menezes, R. V.; Ferreira, M. M.; Sá, J. E. U. Aspectos clínicos e epidemiológicos da raiva bovina apresentados na casuística da Clínica de Bovinos (Oliveira dos Campinhos, Santo Amaro, Bahia), Universidade Federal da Bahia, durante o período de janeiro de 1990 a dezembro de 1999. Revista Brasileira Saúde Produção Animal [Internet]. 2003;4(1):12-17. Disponível em: https://academic.naver.com/article.naver?doc_id=437684339.
https://academic.naver.com/article.naver...
,1111 Lima EF, Riet-Correa F, Castro RS, Gomes AAB, Lima FS. Sinais clínicos, distribuição das lesões no sistema nervoso e epidemiologia da raiva em herbívoros na região Nordeste do Brasil. Pesquisa Veterinária Brasileira. 2005;25(4):250-264. (https://doi.org/10.1590/S0100-736X2005000400011).
https://doi.org/10.1590/S0100-736X200500...
,1313 Galiza GJN, Silva MLCR, Dantas AFM, Simões SVD, Riet-Correa F. Doenças do sistema nervoso de bovinos no semiárido nordestino. Pesquisa Veterinária Brasileira [Internet]. 2010;30(3):267-276. Disponível em: https://www.scielo.br/j/pvb/a/Sp7yJkQgTJ55XLpBqp7JdzH/?lang=pt&format=pdf.
https://www.scielo.br/j/pvb/a/Sp7yJkQgTJ...
,1414 Terra JP, Blume GR, Rabelo RE, Medeiros JT, Rocha CGN, Chagas IN, Aguiar MDS, Sant’ana FJFD. Neurological diseases of cattle in the state of Goiás, Brazil (2010-2017). Pesquisa Veterinária Brasileira. 2018;38(9):1752-1760. (https://doi.org/10.1590/1678-5150-PVB-5768).
https://doi.org/10.1590/1678-5150-PVB-57...
,2727 Radostits OM, Gay CC, Hinchcliff KW, Constable PD. Veterinary medicine. A textbook of the diseases of cattle, horses, sheep, pigs, and goats. 10th ed. Philadelphia: Saunders Elsevier, 2007. 2156p.,2828 Langhor IM, Irigoyen LF, Lemos RAA, Barros CSL. Aspectos epidemiológicos e clínicos e distribuição das lesões histológicas no encéfalo de bovinos com raiva. Ciência Rural. 2003. 33(1):125-131. (https://doi.org/10.1590/S0103-84782003000100020).
https://doi.org/10.1590/S0103-8478200300...
,2929 Rissi DR, Pierezan F, Oliveira-Filho JC, Lucena RB, Carmo PMS, Barros CSL. Abordagem diagnóstica das principais doenças do sistema nervoso de ruminantes e equinos no Brasil. Pesquisa Veterinária Brasileira [Internet]. 2010;30(11):958-967. Disponível em: https://www.readcube.com/articles/10.1590/S0100-736X2010001100010?tab=summary.
https://www.readcube.com/articles/10.159...
,3030 Marcolongo-Pereira C, Sallis ESV, Grecco FB, Raffi MB, Soares MP, Schild AL. Raiva em bovinos na Região Sul do Rio Grande do Sul: epidemiologia e diagnóstico imuno-histoquímico. Pesquisa Veterinária Brasileira. 2011;31(4):331-335. (https://doi.org/10.1590/S0100-736X2011000400010).
https://doi.org/10.1590/S0100-736X201100...
). However, it is known that the variation in these clinical findings and the progression of the virus vary depending on the proximity between the site of inoculation and the brain, concentration of the virus in the inoculum, pathogenicity of the viral strain, and immune status of the animal (3131 Constable PD, Hinchcliff KW, Done SH, Grunberg W. Veterinary medicine. A textbook of the diseases of cattle, horses, sheep, pigs, and goats.11 ed. St. Louis: Elsevier, 2017. 2308p.).

Table 1
Frequency of occurrence of clinical findings observed in cattle diagnosed with rabies (n=84) from 2009 to 2019 at Clínica de Bovinos de Garanhuns-UFRPE.

Considering the hematological findings, the animals diagnosed with rabies showed alteration only in the leukogram, which presented leukocytosis due to neutrophilia, with a slight regenerative shift to the left, a finding also mentioned by Constable (3131 Constable PD, Hinchcliff KW, Done SH, Grunberg W. Veterinary medicine. A textbook of the diseases of cattle, horses, sheep, pigs, and goats.11 ed. St. Louis: Elsevier, 2017. 2308p.). Elevations in white blood cell counts have also been observed in human rabies patients (3232 BRASIL. Ministério da Saúde. Protocolo de Tratamento da Raiva Humana no Brasil. Distrito Federal: Ministério da Saúde, 40 p., 2011.,3333 Alknawy M, Mohammed I, Ulla SN, Aboud AA. First confirmed case of human rabies in Saudi Arabia. IDCases. 2018;12:29-31.). The increase in the neutrophil count in inflammatory processes of viral origin was reported by Tornquist; Rigas (3434 Tornquist SJ, Rigas J. Interpretation of ruminant leukocyte responses. In: Weiss DJ, Wardrop, KJ. Schalm’s Veterinary Hematology. 6th ed. Ames:Wiley-Blackwell; 2010, p.307-313.); Webb; Latimer (3535 Webb Jl, Latimer Ks, Leukocytes. In: Duncan and Prasse’s Veterinary Laboratory Medicine: Clinical Pathology, 5ed. Chichester: Latimer; 2011. p.45-82.). According to Wood and Queiro-Rocha (3636 Wood D, Quiroz-Rocha GF. Normal hematology of cattle. In: Weiss DJ, Wardrop KJ. Schalm’s Veterinary Hematology. 6th ed. Ames:Wiley-Blackwell; 2010, p.829-835), tissue damage, through the release of pro-inflammatory factors, particularly cytokines, triggers the recruitment of leukocytes from the marginal compartment of the bone marrow into the bloodstream, followed by migration to the injured tissue, with the aim of combating the inflammatory and/or infectious process. It should be noted that the rapid demand for neutrophils depletes the stored segmented reserves and stimulates the production and release of young cells.

Among the macroscopic findings, attention is drawn to the hyperemia of the leptomeninges, present in 27% (27/101) of the animals, also reported by Barros et al. (33 Barros CSL, Driemeier D, Dutra IS, Lemos RAA. Doenças do sistema nervoso de bovinos no Brasil. Coleção Vallée, São Paulo, 2006. 207p.), Rissi et al. (2929 Rissi DR, Pierezan F, Oliveira-Filho JC, Lucena RB, Carmo PMS, Barros CSL. Abordagem diagnóstica das principais doenças do sistema nervoso de ruminantes e equinos no Brasil. Pesquisa Veterinária Brasileira [Internet]. 2010;30(11):958-967. Disponível em: https://www.readcube.com/articles/10.1590/S0100-736X2010001100010?tab=summary.
https://www.readcube.com/articles/10.159...
), Braga et al. (3737 Braga JFV, Souza FAL, Franklin FLAA, Beserra EEA, Barreto FM, Araújo Neto JC, Costa FAL, Silva SMMS. Surto de raiva em bovinos no estado do Piauí, Brasil. Acta Veterinaria Brasilica. 2013;7(2):176-179.), and Ecco et al. (3838 Ecco R, Viott AM, Graça DL, Alessi AC. Sistema Nervoso. In: Santos RL, Alessi AC. Patologia veterinária, 2. ed. Rio de Janeiro: Roca; 2017. p.487-572.). Another finding that draws attention is the repletion of the urinary bladder, observed in 50% of the animals. Lima et al. (1111 Lima EF, Riet-Correa F, Castro RS, Gomes AAB, Lima FS. Sinais clínicos, distribuição das lesões no sistema nervoso e epidemiologia da raiva em herbívoros na região Nordeste do Brasil. Pesquisa Veterinária Brasileira. 2005;25(4):250-264. (https://doi.org/10.1590/S0100-736X2005000400011).
https://doi.org/10.1590/S0100-736X200500...
) previously reported urinary bladder dilatation in only 16% of cattle diagnosed with rabies. This reduced number of macroscopic findings agrees with Constable (3131 Constable PD, Hinchcliff KW, Done SH, Grunberg W. Veterinary medicine. A textbook of the diseases of cattle, horses, sheep, pigs, and goats.11 ed. St. Louis: Elsevier, 2017. 2308p.), and Jones, Hunt and King (3939 Jones TC, Hunt RD, King N.W. Patologia Veterinária. 6 ed. São Paulo: Manole; 2000. 1415p.), who state that the lesions are limited to the central nervous system and only detected in the histopathological examination.

The histopathological findings were characterized by a mononuclear inflammatory infiltrate, consisting predominantly of lymphocytes, plasmocytes, and rare macrophages, arranged in the perivascular spaces of the brain and leptomeninges (non-suppurative meningoencephalitis), fig. 02. Eosinophilic viral inclusion corpuscles were observed in the cytoplasm of neurons, sometimes multiple inclusions ranging from 1-10µm in diameter. Additional less frequent findings included focal or diffuse microgliosis, neuronal chromatolysis, neuronal necrosis, and neuroniophagia. In some cases, myelitis and lymphoplasmacytic ganglioneuritis were also observed. In this study, 97% of the cases were positive in direct immunofluorescence (DIF) and in the histopathological examination, when performed. As previously observed in other works on rabies in herbivores (1111 Lima EF, Riet-Correa F, Castro RS, Gomes AAB, Lima FS. Sinais clínicos, distribuição das lesões no sistema nervoso e epidemiologia da raiva em herbívoros na região Nordeste do Brasil. Pesquisa Veterinária Brasileira. 2005;25(4):250-264. (https://doi.org/10.1590/S0100-736X2005000400011).
https://doi.org/10.1590/S0100-736X200500...
), inflammatory alterations and the characteristic Negri bodies can be present throughout the nervous system, but in cattle they tend to be more frequent in the cerebellum (1111 Lima EF, Riet-Correa F, Castro RS, Gomes AAB, Lima FS. Sinais clínicos, distribuição das lesões no sistema nervoso e epidemiologia da raiva em herbívoros na região Nordeste do Brasil. Pesquisa Veterinária Brasileira. 2005;25(4):250-264. (https://doi.org/10.1590/S0100-736X2005000400011).
https://doi.org/10.1590/S0100-736X200500...
). The frequency of appearance of Negri bodies is inversely proportional to the degree of inflammation and they are not present in up to 30% of cases of rabies, as certain strains of the virus do not produce inclusion bodies (1111 Lima EF, Riet-Correa F, Castro RS, Gomes AAB, Lima FS. Sinais clínicos, distribuição das lesões no sistema nervoso e epidemiologia da raiva em herbívoros na região Nordeste do Brasil. Pesquisa Veterinária Brasileira. 2005;25(4):250-264. (https://doi.org/10.1590/S0100-736X2005000400011).
https://doi.org/10.1590/S0100-736X200500...
, 3131 Constable PD, Hinchcliff KW, Done SH, Grunberg W. Veterinary medicine. A textbook of the diseases of cattle, horses, sheep, pigs, and goats.11 ed. St. Louis: Elsevier, 2017. 2308p.). Furthermore, according to Langohr et al. (2828 Langhor IM, Irigoyen LF, Lemos RAA, Barros CSL. Aspectos epidemiológicos e clínicos e distribuição das lesões histológicas no encéfalo de bovinos com raiva. Ciência Rural. 2003. 33(1):125-131. (https://doi.org/10.1590/S0103-84782003000100020).
https://doi.org/10.1590/S0103-8478200300...
) the non-visualization of Negri bodies in some cases of rabies may be directly associated with the survival time of the animal after the infection, that is, the longer the clinical course, the greater the probability of detecting the bodies.

Figure 2
Viral neurological diseases in cattle diagnosed at Clínica de Bovinos de Garanhuns-UFRPE. A) Rabies: Cerebellum. Mononuclear inflammatory infiltrate in the perivascular space and leptomeninges. HE. Obj. 25x. B) Rabies: Cerebellum. Eosinophilic viral inclusion bodies in the cytoplasm of Purkinje neurons. HE. Obj. 40x. C) Malignant catarrhal fever. carotid rete mirabile. Mononuclear inflammatory infiltrate associated with hyaline degeneration in the wall of arterioles (necrotizing vasculitis). HE. Obj. 25x. D) Malignant catarrhal fever. Brain, temporal cortex. Marked mononuclear inflammatory infiltrate in the perivascular space. HE. Obj. 40x. E) Herpetic meningoencephalitis. Frontal cortex, gray matter. Perivascular mononuclear inflammatory infiltrate and Gitter cells in the adjacent neutrophil (malacia). HE. Obj. 40x. F) Herpetic meningoencephalitis. Frontal cortex, gray matter. Eosinophilic intranuclear viral inclusion corpuscle in astrocyte. HE. Obj. 40x.

3.2 Malignant Catarrhal Fever (MCF))

MCF was the second most frequent disease among viral etiologies. Reports by Silva et al. (4040 Silva JA, Moreira EC, Haddad JPA, Modena CM, Tubaldini MAS. Distribuição temporal e espacial da raiva bovina em Minas Gerais, 1976 a 1997. Arquivo Brasileiro de Medicina Veterinária e Zootecnia. 2001.53(3). (https://doi.org/10.1590/S0102-09352001000300001).
https://doi.org/10.1590/S0102-0935200100...
), Souza et al. (4343 Rech RR, Schild AL, Driemeier D, Garmatz SL, Oliveira FN, Riet-Correa F, Barros CSL. Febre catarral maligna em bovinos no Rio Grande do Sul: epidemiologia, sinais clínicos e patologia. Pesquisa Veterinária Brasileira. 2005;25(2):97-105. (https://doi.org/10.1590/S0100-736X2005000200006).
https://doi.org/10.1590/S0100-736X200500...
), and Macêdo et al. (4242 Macêdo JTSA, Riet-Correa F, Simões SVD, Dantas AFM, Nobre VMT. Febre catarral maligna em bovinos na Paraíba. Pesquisa Veterinária Brasileira. 2007;27(7):277-281. (https://doi.org/10.1590/S0100-736X2007000700004).
https://doi.org/10.1590/S0100-736X200700...
), demonstrate that MCF is endemic in the Northeast. The most common manifestations in the current study are distributed in Table 2, as also mentioned in previous works (1010 Lemos RAA, Rech RR, Guimarães EB, Kadri A, Dutra IS. Febre catarral maligna em bovinos do Mato Grosso de Sul e de São Paulo. Ciência Rural. 2005;35(4):932-934. (https://doi.org/10.1590/S0103-84782005000400030).
https://doi.org/10.1590/S0103-8478200500...
,4242 Macêdo JTSA, Riet-Correa F, Simões SVD, Dantas AFM, Nobre VMT. Febre catarral maligna em bovinos na Paraíba. Pesquisa Veterinária Brasileira. 2007;27(7):277-281. (https://doi.org/10.1590/S0100-736X2007000700004).
https://doi.org/10.1590/S0100-736X200700...
,4343 Rech RR, Schild AL, Driemeier D, Garmatz SL, Oliveira FN, Riet-Correa F, Barros CSL. Febre catarral maligna em bovinos no Rio Grande do Sul: epidemiologia, sinais clínicos e patologia. Pesquisa Veterinária Brasileira. 2005;25(2):97-105. (https://doi.org/10.1590/S0100-736X2005000200006).
https://doi.org/10.1590/S0100-736X200500...
,4444 Mendonça FS, Dória RGS, Schein FB, Freitas SH, Nakazato L, Boabaid FM, Paula DAJ, Dutra V, Colodel EM. Febre catarral maligna em bovinos no estado de Mato Grosso. Pesquisa Veterinária Brasileira. 2008;28(3):155-160. Disponível em: https://www.scielo.br/j/pvb/a/sGgyrShqxcmZDRd5dyjHCbT/?lang=pt#.
https://www.scielo.br/j/pvb/a/sGgyrShqxc...
,4545 Preliasco M, Easton MC, Paullier C, Rivero R, Moraes DFS, Godoy I, Dutra V, Nakazato L. Diagnóstico de febre catarral maligna em bovinos do Uruguai. Pesquisa Veterinária Brasileira. 2013;33(1):52-56. (https://doi.org/10.1590/S0100-736X2013000100010).
https://doi.org/10.1590/S0100-736X201300...
,4646 Galvão A, Galvão CF, Caldas AS, Santos AM, D’avila MS, Cid GC, Nogueira VA, Peixoto TC. Febre catarral maligna em bovino no estado do Rio de Janeiro. Revista Brasileira de Medicina Veterinária. 2016;38(1):108-114. Disponível em: https://www.researchgate.net/publication/335128235_Febre_catarral_maligna_em_bovino_no_estado_do_Rio_de_Janeiro_-Relato_de_caso.
https://www.researchgate.net/publication...
,4747 Silva TV, Paulino L R, Afonso J AB, Mendonça CL, Costa NA, Silva NAA, Souto RJC, Coutinho LT, Souza JCA, Cajueiro JFP. Achados clínicos, laboratoriais e anatomopatológicos em bovinos com febre catarral maligna. Revista Acadêmica Ciência Animal. 2017;15(2):397 - 398. (DOI: 10.7213/cienciaanimal.v15iSuppl 2.17523).
https://doi.org/10.7213/cienciaanimal.v1...
). Clinical signs were more evident in animals that survived longer (4848 Spickler A R. 2016. Febre Catarral Maligna. Traduzido e adaptado a situação Brasil por Mendes RE, Schwertz CI e Perosa FF. 2019. Disponível em: http://www.cfsph.iastate.edu/DiseaseInfo/factsheetspt.php?lang=pt.
http://www.cfsph.iastate.edu/DiseaseInfo...
).

Table 2
Frequency of occurrence of clinical findings observed in cattle diagnosed with MCF (n=17) from 2009 to 2019 at Clínica de Bovinos de Garanhuns-UFRPE.

In animals affected by MCF, at the time of hospital discharge, no alterations were observed in the mean values of the erythrogram, as well as in the total leucometry, with the values being within the normal range for the species (4949 Taylor J. A. Leucocyte responses in ruminants. In. Feldman BF, Zinkl JG, Jain NC. Schalm´s veterinary hematology. 5 ed. Philadelphia: Lippincott Williams & Wilkins. 2010. p.391-404.). However, the mean values observed in the leukogram of the neutrophil:lymphocyte ratio are 1:1 and not 1:2, as is generally observed in adult cattle. These findings differ from leukopenia due to agranulocytosis cited in this disease by Constable, (3131 Constable PD, Hinchcliff KW, Done SH, Grunberg W. Veterinary medicine. A textbook of the diseases of cattle, horses, sheep, pigs, and goats.11 ed. St. Louis: Elsevier, 2017. 2308p.) and leukocytosis due to neutrophilia reported by Mendonçaa et al. (4444 Mendonça FS, Dória RGS, Schein FB, Freitas SH, Nakazato L, Boabaid FM, Paula DAJ, Dutra V, Colodel EM. Febre catarral maligna em bovinos no estado de Mato Grosso. Pesquisa Veterinária Brasileira. 2008;28(3):155-160. Disponível em: https://www.scielo.br/j/pvb/a/sGgyrShqxcmZDRd5dyjHCbT/?lang=pt#.
https://www.scielo.br/j/pvb/a/sGgyrShqxc...
). Additionally, in cases of MCF, the increase in the mean value of plasmatic fibrinogen concentration without observation of leukocytosis corroborates with Taylor (4949 Taylor J. A. Leucocyte responses in ruminants. In. Feldman BF, Zinkl JG, Jain NC. Schalm´s veterinary hematology. 5 ed. Philadelphia: Lippincott Williams & Wilkins. 2010. p.391-404.), who reported measuring this protein as the best indicator of inflammatory disease in cattle. According to Eckersall (5050 Eckersall PD. Recent advances and future prospects for the use of acute phase proteins as markers of disease in animals. Revue de Médicine Vétérinaire. 2000;151(7):577-584. (https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.455.3961&rep=rep1&type=pdf).
https://citeseerx.ist.psu.edu/viewdoc/do...
) and O´Mahony et al. (5151 O´Mahony MCO, Healy AM, Harte D, Walshe KG, Torgerson PR, Doherty ML. Milk amyloid A: Correlation with cellular indices of mammary inflammation in cows with normal and raised serum amyloid A. Research in Veterinary Science. 2006:80(2):155-161. Disponível em: https://pubmed.ncbi.nlm.nih.gov/16083930/.
https://pubmed.ncbi.nlm.nih.gov/16083930...
), circulating concentrations of acute phase proteins are related to the severity of organ dysfunction and, therefore, their quantification readily provides a means of assessing the presence and extent of the inflammatory process. Thus, the fibrinogen response probably stems from the intense inflammatory reaction resulting from generalized vasculitis, which represents a severe inflammatory process in cases of MCF.

Necropsy findings included fibrin-necrotic material in the mucous membranes of the respiratory tract (06/19), hyperemia of the telencephalic vessels (05/19), tracheitis (03/19) fig. 01, hyperemia of the leptomeningeal vessels (04/19), edema of the folds of the abomasum and mesentery (01/19), hepatomegaly (04/19), pulmonary edema (04/19), rumenitis/abomasitis/reticulitis (02 /19), petechiae and cardiac suffusions (3/19), and hypopyon (5/19), as also found in other studies (4343 Rech RR, Schild AL, Driemeier D, Garmatz SL, Oliveira FN, Riet-Correa F, Barros CSL. Febre catarral maligna em bovinos no Rio Grande do Sul: epidemiologia, sinais clínicos e patologia. Pesquisa Veterinária Brasileira. 2005;25(2):97-105. (https://doi.org/10.1590/S0100-736X2005000200006).
https://doi.org/10.1590/S0100-736X200500...
,4545 Preliasco M, Easton MC, Paullier C, Rivero R, Moraes DFS, Godoy I, Dutra V, Nakazato L. Diagnóstico de febre catarral maligna em bovinos do Uruguai. Pesquisa Veterinária Brasileira. 2013;33(1):52-56. (https://doi.org/10.1590/S0100-736X2013000100010).
https://doi.org/10.1590/S0100-736X201300...
,4646 Galvão A, Galvão CF, Caldas AS, Santos AM, D’avila MS, Cid GC, Nogueira VA, Peixoto TC. Febre catarral maligna em bovino no estado do Rio de Janeiro. Revista Brasileira de Medicina Veterinária. 2016;38(1):108-114. Disponível em: https://www.researchgate.net/publication/335128235_Febre_catarral_maligna_em_bovino_no_estado_do_Rio_de_Janeiro_-Relato_de_caso.
https://www.researchgate.net/publication...
,5252 Peixoto TC, Cunha VAF, Silva DN, Farias SS, Madureira KM. Febre Catarral Maligna em bovino no estado da Bahia. Enciclopédia Biosfera. 2015;11(21):1092-1101. Disponível em: https://conhecer.org.br/ojs/index.php/biosfera/article/view/1831.
https://conhecer.org.br/ojs/index.php/bi...
, 5353 Silva Filho GB, Chaves HAS, Aires LD, Nakazato L, Colodel EM, Freitas SH, Dória RGS, Evêncio Neto E, Mendonça FS. Febre catarral maligna em bovinos no Agreste de Pernambuco, Medicina Veterinária (UFRPE). 2017;11(3):192-196. (https://doi.org/10.26605/medvet-n3-1793).
https://doi.org/10.26605/medvet-n3-1793...
). In the cases reported in Goiás by Terra et al. (1414 Terra JP, Blume GR, Rabelo RE, Medeiros JT, Rocha CGN, Chagas IN, Aguiar MDS, Sant’ana FJFD. Neurological diseases of cattle in the state of Goiás, Brazil (2010-2017). Pesquisa Veterinária Brasileira. 2018;38(9):1752-1760. (https://doi.org/10.1590/1678-5150-PVB-5768).
https://doi.org/10.1590/1678-5150-PVB-57...
), there were no significant macroscopic findings.

Figure 1
Viral neurological diseases in cattle diagnosed at Clínica de Bovinos de Garanhuns-UFRPE. A) Rabies: Animal in recumbency with pedaling movements B) Rabies: Urinary bladder distension. C) Malignant catarrhal fever: Erosions/ulcerations in the region of the glottis and epiglottis. D) Malignant catarrhal fever: Erosions on the tongue. E) Herpetic meningoencephalitis: Absent anal sphincter reflex. F) Herpetic meningoencephalitis: Reduced sensitivity of the face.

Histopathological findings in the nervous system were characterized by a mononuclear inflammatory infiltrate, composed of lymphocytes, plasmocytes, and macrophages, and hyaline degeneration of the walls of arterioles (necrotizing vasculitis), particularly those of small caliber present in the carotid rete mirabile, fig. 02. The inflammatory infiltrate sometimes extended to perivascular spaces and leptomeninges. Vascular lesions were also observed in arterioles present in other tissues, such as the kidneys, liver, lymph nodes, and mucous membrane of the alimentary, respiratory, urinary, and genital tracts, almost always associated with ulceration of the overlying epithelium. The visualization of multisystem vasculitis, accumulations of mononuclear inflammatory cells in various tissues, and necrosis of the lining epithelia strongly contribute to the establishment of the histopathological diagnosis of MCF (5454 Garmatz SL, Irigoyen LF, Rech RR, Brown CC, Zhang J, Barros CSL. Febre catarral maligna em bovinos no Rio Grande do Sul: transmissão experimental para bovinos e caracterização do agente etiológico. Pesquisa Veterinária Brasileira. 2004;24(2):93-106. (https://doi.org/10.1590/S0100-736X2004000200009).
https://doi.org/10.1590/S0100-736X200400...
) as described in the states of Mato Grosso do Sul and São Paulo by Lemos et al. (1010 Lemos RAA, Rech RR, Guimarães EB, Kadri A, Dutra IS. Febre catarral maligna em bovinos do Mato Grosso de Sul e de São Paulo. Ciência Rural. 2005;35(4):932-934. (https://doi.org/10.1590/S0103-84782005000400030).
https://doi.org/10.1590/S0103-8478200500...
), in Paraíba by Macêdo et al. (4242 Macêdo JTSA, Riet-Correa F, Simões SVD, Dantas AFM, Nobre VMT. Febre catarral maligna em bovinos na Paraíba. Pesquisa Veterinária Brasileira. 2007;27(7):277-281. (https://doi.org/10.1590/S0100-736X2007000700004).
https://doi.org/10.1590/S0100-736X200700...
), in Rio de Janeiro by Galvão et al. (4646 Galvão A, Galvão CF, Caldas AS, Santos AM, D’avila MS, Cid GC, Nogueira VA, Peixoto TC. Febre catarral maligna em bovino no estado do Rio de Janeiro. Revista Brasileira de Medicina Veterinária. 2016;38(1):108-114. Disponível em: https://www.researchgate.net/publication/335128235_Febre_catarral_maligna_em_bovino_no_estado_do_Rio_de_Janeiro_-Relato_de_caso.
https://www.researchgate.net/publication...
), in Espírito Santo by Carmo et al. (5555 Carmo PMS, Oliveira KD, Barioni G, Oliveira-Filho JC, Souza TD. Malignant catarrhal fever in a calf in Espírito Santo State, Brazil: report of the first case. Brazilian Journal of Veterinary Pathology, 2011;4(1):44-46. Disponível em: https://bjvp.org.br/wp-content/uploads/2015/07/V.4-N.1-08-20881_2011_3_16_5_37.pdf.
https://bjvp.org.br/wp-content/uploads/2...
), and in Bahia by Peixoto et al. (5252 Peixoto TC, Cunha VAF, Silva DN, Farias SS, Madureira KM. Febre Catarral Maligna em bovino no estado da Bahia. Enciclopédia Biosfera. 2015;11(21):1092-1101. Disponível em: https://conhecer.org.br/ojs/index.php/biosfera/article/view/1831.
https://conhecer.org.br/ojs/index.php/bi...
).

3.3 Herpesvirus meningoencephalitis

In the current work, among diseases of viral etiology, meningoencephalitis due to herpesvirus had a frequency of 7.7% (10/604), being lower than rabies and MCF, as reported in other regions in the northeastern semi-arid region (1313 Galiza GJN, Silva MLCR, Dantas AFM, Simões SVD, Riet-Correa F. Doenças do sistema nervoso de bovinos no semiárido nordestino. Pesquisa Veterinária Brasileira [Internet]. 2010;30(3):267-276. Disponível em: https://www.scielo.br/j/pvb/a/Sp7yJkQgTJ55XLpBqp7JdzH/?lang=pt&format=pdf.
https://www.scielo.br/j/pvb/a/Sp7yJkQgTJ...
). This result differs from several retrospective studies of diseases that affect the central nervous system, carried out in different regions of Brazil in recent years, in which the highest occurrences are predominantly attributed to rabies followed by meningoencephalitis due to herpesvirus. Possibly, the low occurrence may be related to the difficulty of diagnosis, since it requires laboratory resources, such as the Polymerase Chain Reaction or immunohistochemistry.

The clinical signs observed are shown in Table 3. The findings are similar to those described by other authors in cases of the disease (55 Ribas NLKS, Carvalho RI, Santos AC, Valençoela RA, Gouveia AF, Castro MB, Mori AE, Lemos RAA. Doenças do sistema nervoso de bovinos no Mato Grosso do Sul: 1082 casos. Pesquisa Veterinária Brasileira. 2013;33(10):1183-1194. (https://doi.org/10.1590/S0100-736X2013001000003).
https://doi.org/10.1590/S0100-736X201300...
,1313 Galiza GJN, Silva MLCR, Dantas AFM, Simões SVD, Riet-Correa F. Doenças do sistema nervoso de bovinos no semiárido nordestino. Pesquisa Veterinária Brasileira [Internet]. 2010;30(3):267-276. Disponível em: https://www.scielo.br/j/pvb/a/Sp7yJkQgTJ55XLpBqp7JdzH/?lang=pt&format=pdf.
https://www.scielo.br/j/pvb/a/Sp7yJkQgTJ...
,5656 Colodel EM, Nakazato L, Weiblen R, Mello RM, Silva RRP, Souza MA, Oliveira Filho JÁ, Caron L. Meningoencefalite necrosante em bovinos causada por herpesvírus bovino no estado de Mato Groso do Sul, Brasil. Ciência Rural. 2002;32(2):293-298. (https://doi.org/10.1590/S0103-84782002000200018).
https://doi.org/10.1590/S0103-8478200200...
,5757 Rissi DR, Oliveira FN, Rech RR, Pierezan F, Lemos RAA, Barros CSL. Epidemiologia, sinais clínicos e distribuição das lesões encefálicas em bovinos afetados por meningoencefalite por herpesvírus bovino-5. Pesquisa Veterinária Brasileira. 2006;26(2):123-132. (https://doi.org/10.1590/S0100-736X2006000200010).
https://doi.org/10.1590/S0100-736X200600...
,5858 Riet-Correa G, Duarte MD, Barbosa JD, Oliveira CMC, Cerqueira VD, Brito MF, Riet-Correa F. Meningoencefalite e polioencefalomalacia causada por Herpesvírus bovino-5 no Estado do Pará. Pesquisa Veterinária Brasileira. 2006;26(1):44-46. Disponível em: https://www.scielo.br/j/pvb/a/6mDLxnV8NCf9xKZKtdSzY4w/?format=pdf⟨=pt.
https://www.scielo.br/j/pvb/a/6mDLxnV8NC...
,5959 Oliveira JS, Albuquerque RF, Aguiar-Filho CR, De Arruda LP, Colodel EM, Rocha BP, Mendonça FS. Meningoencefalite necrosante em bovinos associada ao herpesvírus bovino-5 em Pernambuco-Brasil. Acta Scientiae Veterinariae. 2014;42(1):1-5. Disponível em: https://www.redalyc.org/pdf/2890/289039188006.pdf.
https://www.redalyc.org/pdf/2890/2890391...
). These symptoms, as well as their intensity, varied between animals and throughout evolution. In experimental infection, some animals did not exhibit clinical manifestations, however the histopathological examination confirmed that all calves studied exhibited an encephalic inflammatory process, indicating that the encephalitis caused by BoHV-5 may be mild and asymptomatic (6060 Isernhagen A.J., Cosenza M., Costa M.C.C., Médici K.C., Balarin M.R.S., Bracarense A.P.F.R.L., Alfieri A.A. & Lisbôa J.A.N. 2011. Asymtomatic encephalitis in calves experimentally infected with bovine herpesvirus-5. Can. Vet. J. 52(12):1312-1318. PMid:22654135.).

Table 3
Frequency of occurrence of clinical findings observed in cattle diagnosed with herpetic meningoencephalitis (n=09) from 2009 to 2019 at Clínica de Bovinos de Garanhuns-UFRPE.

The animals diagnosed with herpetic meningoencephalitis showed neutrophilic leukocytosis, with a slight regenerative left shift and plasma fibrinogen and erythrogram values within the normal range. Results consistent with a tendency to leukocytosis accompanied by increased segmented neutrophils and normal plasma fibrinogen levels were reported by Lisbôa et al. (6161 Lisbôa JAN, Isernhagen AJ, Borges AS, Amorim RM, Balarin MRS, Lunardi M, Alfieri AA. Hematological and Cerebrospinal Fluid Changes in Cattle Naturally and Experimentally Infected with the Bovine Herpesvirus 5. Brazilian Archives of Biology and Technology. 2009;52:69-76. (https://doi.org/10.1590/S1516-89132009000700010).
https://doi.org/10.1590/S1516-8913200900...
). In these cases, the increase in the number of circulating neutrophils is due to the stimulus caused by the stressors that trigger meningoencephalitis (6262 Rissi DR, Rech RR, Flores EF, Kommer SGD, Barros CSL. Meningoencefalite por herpesvírus bovino-5. Pesquisa Veterinária Brasileira. 2007;27(7):251-260. (https://doi.org/10.1590/S0100-736X2007000700001).
https://doi.org/10.1590/S0100-736X200700...
).

In most of the cases observed in this study, necropsy findings were not prominent, as described by Rissi et al. (57) and Oliveira et al. (59). When present, such findings consisted of multifocal yellowish and soft areas in the telencephalic cortices, characteristic of cerebral gray matter malacia, and hyperemia of the leptomeningeal vessels (63).

The histopathological findings were characterized by a mononuclear inflammatory infiltrate consisting of lymphocytes, plasma cells, and macrophages in the perivascular spaces and extending to the neuropil and adjacent leptomeninges. In the gray matter, retracted, hypereosinophilic neuronal cell bodies with a pyknotic nucleus (cortical laminar necrosis) were observed, sometimes associated with neuroniophagia, gliosis, vasculitis, edema, and multifocal areas of vacuolization and malacia, permeated by Gitter cells. Occasional astrocytes and neurons with eosinophilic viral intranuclear inclusion bodies were also seen (Fig. 2). Cases of herpetic meningoencephalitis present areas of malacia as the main histopathological finding (5656 Colodel EM, Nakazato L, Weiblen R, Mello RM, Silva RRP, Souza MA, Oliveira Filho JÁ, Caron L. Meningoencefalite necrosante em bovinos causada por herpesvírus bovino no estado de Mato Groso do Sul, Brasil. Ciência Rural. 2002;32(2):293-298. (https://doi.org/10.1590/S0103-84782002000200018).
https://doi.org/10.1590/S0103-8478200200...
,6363 Perez SE, Bretschneider G, Leunda MR, Osório FA, Flores EF, Odeón AC. Primary infection, latency, and reactivation of Bovine Herpesvirus type 5 in the bovine nervous system. Veterinary Pathology. 2002;39(4):437-444. (https://doi.org/10.1354/vp.39-4-437).
https://doi.org/10.1354/vp.39-4-437...
,6464 Elias F, Schild AL, Riet-Correa F. Meningoencefalite e encefalomalacia por herpesvírus bovino-5: distribuição das lesões no sistema nervoso central de bovinos naturalmente infectados. Pesquisa Veterinária Brasileira. 2004;24(3):123-131. (https://doi.org/10.1590/S0100-736X2004000300003).
https://doi.org/10.1590/S0100-736X200400...
), most often located in the frontal cortex, although other regions can be affected (6464 Elias F, Schild AL, Riet-Correa F. Meningoencefalite e encefalomalacia por herpesvírus bovino-5: distribuição das lesões no sistema nervoso central de bovinos naturalmente infectados. Pesquisa Veterinária Brasileira. 2004;24(3):123-131. (https://doi.org/10.1590/S0100-736X2004000300003).
https://doi.org/10.1590/S0100-736X200400...
). This is probably related to the usual route of access of the virus to the nervous system through the olfactory nerves (6363 Perez SE, Bretschneider G, Leunda MR, Osório FA, Flores EF, Odeón AC. Primary infection, latency, and reactivation of Bovine Herpesvirus type 5 in the bovine nervous system. Veterinary Pathology. 2002;39(4):437-444. (https://doi.org/10.1354/vp.39-4-437).
https://doi.org/10.1354/vp.39-4-437...
).

Animals that simultaneously developed polioencephalomalacia and herpesvirus meningoencephalitis had more pronounced malacia lesions, corroborating the findings of David et al. (6565 David N., Hübner S.O., Riet-Correa F., Halfen D. & Lemos R.A.A. 2007. Reactivation of latent bovine herpesvirus type 5 in cattle with polioencephalomalacia induced by ammonium sulphate. Pesq. Vet. Bras. 27:435-441.). Although the characteristic lesion of non-suppurative meningoencephalitis is attributed to BoHV5, the same lesion may also be present in some cases of BoHV1 infection due to its tropism for the central nervous system, as well as cases of rabies and malignant bluetongue (033 Barros CSL, Driemeier D, Dutra IS, Lemos RAA. Doenças do sistema nervoso de bovinos no Brasil. Coleção Vallée, São Paulo, 2006. 207p.). Therefore, it is necessary to confirm the infection by means of diagnostic techniques that allow the distinction not only between different neurological disorders, but also between types 1 and 5 of bovine alpha-herpesvirus. The distribution of diseases of neurological origin may vary due to the regional particularities of each place where it occurs. For this reason, it is necessary to identify regional circulation agents so that the appropriate strategic actions can be conducted to minimize losses (1515 Queiroz GR, Oliveira RAM, Flaiban KKMC, Di Santis GW, Bracarense APFRL, Headley SA, Alfieri AA, Lisbôa JAN. Diagnóstico diferencial das doenças neurológicas dos bovinos no estado do Paraná. Pesquisa Veterinária Brasileira. 2018;38(7):1264-1277. (https://doi.org/10.1590/1678-5150-PVB-5429).
https://doi.org/10.1590/1678-5150-PVB-54...
).

4. Conclusions

The clinical findings of neurological diseases of viral etiology are very varied and nonspecific, and the anatomopathological findings, combined with laboratory methods, are of fundamental importance for establishing the diagnosis. The high frequency of rabies cases in this study demonstrates the importance of this disease for cattle farming, as well as for public health, as it is a lethal zoonosis for both species, and the adoption of preventive health measures in the region is vital. It is important to include malignant bluetongue and herpetic meningoencephalitis in the differential diagnosis of neurological diseases in the region, as well as disseminating the adoption of sanitary measures.

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Publication Dates

  • Publication in this collection
    26 June 2023
  • Date of issue
    2023

History

  • Received
    19 Dec 2022
  • Accepted
    11 Apr 2023
  • Published
    17 May 2023
Universidade Federal de Goiás Universidade Federal de Goiás, Escola de Veterinária e Zootecnia, Campus II, Caixa Postal 131, CEP: 74001-970, Tel.: (55 62) 3521-1568, Fax: (55 62) 3521-1566 - Goiânia - GO - Brazil
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