Occurrence of abortions induced by Neospora caninum in dairy cattle from Santa Catarina, southern Brazil

Ocorrência de abortamentos induzidos por Neospora caninum em vacas de leite de Santa Catarina, sul do Brasil

Cesar Augusto Barbosa de Macedo Madlaine Frigo Silveira Barbosa de Macedo Ana Carolina Miura Alessandra Taroda Sergio Tosi Cardim Elisabeth Ann Innes Frank Katzer German Jose Cantón Francesca Chianini Selwyn Arlington Headley João Luis Garcia About the authors

Abstract

The aim of the present study was to investigate the occurrence of N. caninum associated with abortions of dairy cattle from Santa Catarina state, southern Brazil by using enzyme-linked immunosorbent assay (ELISA), immunohistochemistry (IHC), and polymerase chain reaction (PCR). Blood from dairy cows that aborted along with intrathoracic fluid and tissue samples (brain, heart, liver, and lung) from their fetuses were collected and used for serology; PCR, histopathological, and immunohistochemistry (IHC) evaluations were also conducted. Twenty-one cows (51.2%) out of 41, and eight fetuses (26.7%) out of 30 were ELISA (HerdCheck, IDEXX) positive for N. caninum. Dams > 36 months of age had a higher risk of being serum positive than younger animals. PCR and IHC revealed that 38.8% (14/36) and 25.0% (9/36) of the fetuses were positive for N. caninum, respectively for each of the tests. Seropositive cows had a higher frequency of fetuses that were also positive by either intrathoracic fluid, PCR, or IHC. In summary, the present study observed a high frequency of N. caninum in abortions from dairy cows from southern Brazil, with a higher N. caninum prevalence found in cows that were older than 36 months. In addition, serology, PCR, and IHC should be used all together for better diagnosis of neosporosis in cattle.

Keywords:
Neosporosis; fetuses; lesion; serology; cattle

Resumo

O objetivo deste estudo foi avaliar a ocorrência de N. caninum associado a abortamentos em vacas de leite do estado de Santa Catarina, sul do Brasil pelo uso das técnicas de ELISA (HerdCheck, IDEXX), reação em cadeia pela polimerase (PCR) e imunohistoquímica (IHC). O sangue das vacas leiteiras que abortaram, bem como, o líquido intratorácico e amostras de tecidos (cérebro, coração, fígado e pulmão) de seus fetos foram coletados e usados para sorologia, PCR (Np21+ e Np6+), e IHC. Vinte e uma vacas (51,2%) de um total de 41, bem como, oito fetos (26,7%) de um total de 30 foram positivos no ELISA (IDEXX) para N. caninum. As vacas > 36 meses de idade tiveram um maior risco de serem soropositivas do que os animais mais jovens. PCR e IHC revelaram que 38,8% e 25,0% dos fetos foram positivos para N. caninum, respectivamente para cada um dos testes. As vacas soropositivas tiveram uma maior frequência de fetos que também foram positivos no fluído intratorácico, na PCR ou na IHC. Em resumo, o presente estudo observou uma alta frequência de N. caninum em abortos de vacas leiteiras na região estudada, com maior prevalência de N. caninum em vacas com mais de 36 meses de idade. Além disso, sorologia, PCR e IHC deveriam ser utilizadas ​​conjuntamente para melhor diagnóstico de neosporose em bovinos.

Palavras-chaves:
Neosporose; bovinos; sorologia; vacas; diagnóstico

Introduction

Neospora caninum is a protozoan parasite of animals that may have been misdiagnosed as Toxoplasma gondii until 1988 when it was recognized as a distinct Species (DUBEY et al., 2007Dubey JP, Schares G, Ortega-Mora LM. Epidemiology and control of neosporosis and Neospora caninum. Clin Microbiol Rev 2007; 20(2): 323-367. PMid:17428888. http://dx.doi.org/10.1128/CMR.00031-06.
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, 2011Dubey JP, Jenkins MC, Rajendran C, Miska K, Ferreira LR, Martins J, et al. Gray wolf (Canis lupus) is a natural definitive host for Neospora caninum. Vet Parasitol 2011; 181(2-4): 382-387. PMid:21640485. http://dx.doi.org/10.1016/j.vetpar.2011.05.018.
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). Dogs (Canis lupus familiaris), coyotes (Canis latrans), dingoes (Canis lupus dingo), and gray wolfs (C. lupus) are considered as definitive hosts for this parasite (DUBEY et al., 2011Dubey JP, Jenkins MC, Rajendran C, Miska K, Ferreira LR, Martins J, et al. Gray wolf (Canis lupus) is a natural definitive host for Neospora caninum. Vet Parasitol 2011; 181(2-4): 382-387. PMid:21640485. http://dx.doi.org/10.1016/j.vetpar.2011.05.018.
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; GONDIM et al., 2004Gondim LF, McAllister MM, Pitt WC, Zemlicka DE. Coyotes (Canis latrans) are definitive hosts of Neospora caninum. Int J Parasitol 2004; 34(2): 159-161. PMid:15037103. http://dx.doi.org/10.1016/j.ijpara.2004.01.001.
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; KING et al., 2010King JS, Slapeta J, Jenkins DJ, Al-Qassab SE, Ellis JT, Windsor PA. Australian dingoes are definitive hosts of Neospora caninum. Int J Parasitol 2010; 40(8): 945-950. PMid:20149793. http://dx.doi.org/10.1016/j.ijpara.2010.01.008.
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; McALLISTER et al., 1998McAllister MM, Dubey JP, Lindsay DS, Jolley WR, Wills RA, McGuire AM. Dogs are definitive hosts of Neospora caninum. Int J Parasitol 1998; 28(9): 1473-1478. PMid:9770635. http://dx.doi.org/10.1016/S0020-7519(98)00138-6.
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). Additionally, several livestock and wild animal species have been identified as intermediate hosts of N. caninum (DUBEY & LINDSAY, 1996Dubey JP, Lindsay DS. A review of Neospora caninum and neosporosis. Vet Parasitol 1996; 67(1-2): 1-59. PMid:9011014. http://dx.doi.org/10.1016/S0304-4017(96)01035-7.
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). Moreover, surveys conducted in several countries have identified N. caninum infections as the major cause of bovine abortions (ANDERSON et al., 2000Anderson ML, Andrianarivo AG, Conrad PA. Neosporosis in cattle. Anim Reprod Sci 2000; 60-61: 417-431. PMid:10844212. http://dx.doi.org/10.1016/S0378-4320(00)00117-2.
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), particularly among dairy cattle (DUBEY & LINDSAY, 1996Dubey JP, Lindsay DS. A review of Neospora caninum and neosporosis. Vet Parasitol 1996; 67(1-2): 1-59. PMid:9011014. http://dx.doi.org/10.1016/S0304-4017(96)01035-7.
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).

N. caninum can be either transmitted postnatally (horizontal) by the ingestion of food and/or drinking water contaminated with sporulated oocysts, or transplacentally (vertical) (DUBEY, 2005Dubey JP. Neosporosis in cattle. Vet Clin North Am Food Anim Pract 2005; 21(2): 473-483. PMid:15955441. http://dx.doi.org/10.1016/j.cvfa.2005.03.004.
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; DUBEY et al., 2007Dubey JP, Schares G, Ortega-Mora LM. Epidemiology and control of neosporosis and Neospora caninum. Clin Microbiol Rev 2007; 20(2): 323-367. PMid:17428888. http://dx.doi.org/10.1128/CMR.00031-06.
http://dx.doi.org/10.1128/CMR.00031-06...
). Vertical transmission of N. caninum from one generation to the next generation of cattle appears to be the major route by which the infection is maintained within herds (BILDFELL et al., 1994Bildfell R, Davidson J, Dubey JP. Neospora-induced protozoal bovine abortion in Prince Edward Island. Can Vet J 1994; 35(2): 122. PMid:8069823.; HALL et al., 2005Hall CA, Reichel MP, Ellis JT. Neospora abortions in dairy cattle: diagnosis, mode of transmission and control. Vet Parasitol 2005; 128(3-4): 231-241. PMid:15740860. http://dx.doi.org/10.1016/j.vetpar.2004.12.012.
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; WOUDA, 2000Wouda W. Diagnosis and epidemiology of bovine neosporosis: a review. Vet Q 2000; 22(2): 71-74. PMid:10789513. http://dx.doi.org/10.1080/01652176.2000.9695028.
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). Vertical transmission may result in fetuses that may die in utero, be reabsorbed, mummified, autolyzed, stillborn, born alive with clinical signs, or born clinically normal but persistently infected (DUBEY, 2003Dubey JP. Review of Neospora caninum and neosporosis in animals. Korean J Parasitol 2003; 41(1): 1-16. PMid:12666725. http://dx.doi.org/10.3347/kjp.2003.41.1.1.
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; HADDAD et al., 2005Haddad JP, Dohoo IR, Van Leewen JA. A review of Neospora caninum in dairy and beef cattle--a Canadian perspective. Can Vet J 2005; 46(3): 230-243. PMid:15884645.).

The diagnosis of N. caninum-induced abortions is often expensive and sometimes difficult, either because of the absence of fetus and placenta, especially for beef cattle, or the use of just serology, what may be inconclusive. Serological examination of the dam and fetus (DUBEY & LINDSAY, 1996Dubey JP, Lindsay DS. A review of Neospora caninum and neosporosis. Vet Parasitol 1996; 67(1-2): 1-59. PMid:9011014. http://dx.doi.org/10.1016/S0304-4017(96)01035-7.
http://dx.doi.org/10.1016/S0304-4017(96)...
), observation of histopathological lesions, immunohistochemistry (ANDERSON et al., 2000Anderson ML, Andrianarivo AG, Conrad PA. Neosporosis in cattle. Anim Reprod Sci 2000; 60-61: 417-431. PMid:10844212. http://dx.doi.org/10.1016/S0378-4320(00)00117-2.
http://dx.doi.org/10.1016/S0378-4320(00)...
), and parasite detection by PCR techniques (COLLANTES-FERNANDEZ et al., 2006Collantes-Fernández E, Arnáiz-Seco I, Burgos BM, Rodríguez-Bertos A, Aduriz G, Fernández-García A, et al. Comparison of Neospora caninum distribution, parasite loads and lesions between epidemic and endemic bovine abortion cases. Vet Parasitol 2006; 142(1-2): 187-191. PMid:16884852. http://dx.doi.org/10.1016/j.vetpar.2006.05.030.
http://dx.doi.org/10.1016/j.vetpar.2006....
) are tools that may contribute to a successful diagnosis of bovine Neospora abortion.

In Brazil, N. caninum was considered an important abortifacient agent in cattle (CORBELLINI et al., 2002Corbellini LG, Driemeier D, Cruz CF, Gondim LF, Wald V. Neosporosis as a cause of abortion in dairy cattle in Rio Grande do Sul, southern Brazil. Vet Parasitol 2002; 103(3): 195-202. PMid:11750112. http://dx.doi.org/10.1016/S0304-4017(01)00600-8.
http://dx.doi.org/10.1016/S0304-4017(01)...
; SANTOS et al., 2005bSantos APME, Navarro IT, Freire RL, Vidotto O, Bracarense APFRL. Neospora caninum in dairy cattle in Paraná State, Brazil: histological and immunohistochemical analysis in fetuses. Semina: Cienc Agrar 2005b; 26(4): 559-562. http://dx.doi.org/10.5433/1679-0359.2005v26n4p559.
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; CORBELLINI et al., 2006Corbellini LG, Pescador CA, Frantz F, Wunder E, Steffen D, Smith DR, et al. Diagnostic survey of bovine abortion with special reference to Neospora caninum infection: importance, repeated abortion and concurrent infection in aborted fetuses in Southern Brazil. Vet J 2006; 172(1): 114-120. PMid:16772136. http://dx.doi.org/10.1016/j.tvjl.2005.03.006.
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; ORLANDO et al., 2013Orlando DR, Costa RC, Soares BA, Oliveira NSC, Nascimento LC, Peconick AP, et al. Neospora caninum abortions in cattle in southern Minas Gerais, Brazil. Pesq Vet Bras 2013; 33(11): 1332-1338. http://dx.doi.org/10.1590/S0100-736X2013001100008.
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; PESCADOR et al., 2007Pescador CA, Corbellini LG, Oliveira EC, Raymundo DL, Driemeier D. Histopathological and immunohistochemical aspects of Neospora caninum diagnosis in bovine aborted fetuses. Vet Parasitol 2007; 150(1-2): 159-163. PMid:17904290. http://dx.doi.org/10.1016/j.vetpar.2007.08.028.
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; CABRAL et al., 2009Cabral AD, Camargo CN, Galleti NT, Okuda LH, Pituco EM, Fava CD. Diagnosis of Neospora caninum in bovine fetuses by histology, immunohistochemistry, and nested-PCR. Rev Bras Parasitol Vet 2009; 18(4): 14-19. PMid:20040203. http://dx.doi.org/10.4322/rbpv.01804003.
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). Corbellini et al. (2002)Corbellini LG, Driemeier D, Cruz CF, Gondim LF, Wald V. Neosporosis as a cause of abortion in dairy cattle in Rio Grande do Sul, southern Brazil. Vet Parasitol 2002; 103(3): 195-202. PMid:11750112. http://dx.doi.org/10.1016/S0304-4017(01)00600-8.
http://dx.doi.org/10.1016/S0304-4017(01)...
showed in Rio Grande do Sul state, southern Brazil, 81% of the aborted fetuses with brain lesions suggestive of N. caninum. Santos et al. (2005b)Santos APME, Navarro IT, Freire RL, Vidotto O, Bracarense APFRL. Neospora caninum in dairy cattle in Paraná State, Brazil: histological and immunohistochemical analysis in fetuses. Semina: Cienc Agrar 2005b; 26(4): 559-562. http://dx.doi.org/10.5433/1679-0359.2005v26n4p559.
http://dx.doi.org/10.5433/1679-0359.2005...
showed by immunohistochemistry this parasite in eight out of 30 fetuses coming from 22 dairy herds from Paraná state, those fetuses were between 3 to 7 months of age. Additionally, in Sao Paulo state, 24.8% of fetuses were found infected with N. caninum (CABRAL et al., 2009Cabral AD, Camargo CN, Galleti NT, Okuda LH, Pituco EM, Fava CD. Diagnosis of Neospora caninum in bovine fetuses by histology, immunohistochemistry, and nested-PCR. Rev Bras Parasitol Vet 2009; 18(4): 14-19. PMid:20040203. http://dx.doi.org/10.4322/rbpv.01804003.
http://dx.doi.org/10.4322/rbpv.01804003...
).

Those previous studies, characterized N. caninum by either histopathology or immunohistochemistry (IHC) of aborted fetuses. Thus, the aim of the present study was to investigate the occurrence of N. caninum associated with abortions of dairy cattle from Santa Catarina state, southern Brazil by using enzyme-linked immunosorbent assay (ELISA), immunohistochemistry (IHC), and polymerase chain reaction (PCR).

Material and Methods

Study area and sampling

The survey was done in the city of Presidente Getulio (27° 03’ 03” S, 49° 37’ 22” N), located at an altitude of 255 m in the Itajaí river valley of the state of Santa Catarina, southern Brazil. Forty-one dairy cows (Bos taurus) from Holstein and Jersey breed and their aborted fetuses derived from thirty-five dairy farms, were analyzed. At first sampling blood of cows and tissues and fluids of aborted fetuses were collected. Further, all farms were revisited to obtain a second blood sample from the cows 30 days after abortion. This project was approved by Animal Ethical Committee from Universidade Estadual de Londrina (number 18/09).

Blood, intrathoracic fluid and tissue samples

Blood samples, with and without EDTA, were collected from the dairy cows that aborted, while intrathoracic fluid was obtained from their fetuses. The white blood cells (WBC) were separated by centrifugation (550xg – 10min), and used for DNA extraction and in PCR assays. Additionally, a pool of tissue fragments (brain, heart, liver, and lung) from each fetus was obtained and used in PCR assays. All tissue samples were homogenized in 10 ml of saline solution (0.14M NaCl), the homogenate filtered through two layers of gauze, after which 2 ml were used for DNA extraction.

Anti-Neospora caninum antibody detection

Antibodies against N. caninum were detected using a commercial indirect ELISA test (HerdCheck, IDEXX) that used N. caninum tachyzoite-soluble proteins as the antigen. Sera from cows and fluid from fetuses were diluted 1:100 and 1:25 (WOUDA et al., 1997Wouda W, Dubey JP, Jenkins MC. Serological diagnosis of bovine fetal neosporosis. J Parasitol 1997; 83(3): 545-547. PMid:9194848. http://dx.doi.org/10.2307/3284431.
http://dx.doi.org/10.2307/3284431...
), respectively. The presence or absence of antibodies to N. caninum was determined by calculating the ratio of the result for the sample to the result for the positive control (S/P) for each sample. The ratio (S/P) was calculated as follows: (sample optical density – mean negative control)/(mean positive control – mean negative control). Serum samples with a ratio (S/P) < 0.50 were classified as negative and ratio (S/P) ≥ 0.50 as positive. The sensitivity (Se) and specificity (Sp) of the test were 99% and 97.5%, respectively (VON BLUMRODER et al., 2004Von Blumroder D, Schares G, Norton R, Williams DJ, Esteban-Redondo I, Wright S, et al. Comparison and standardisation of serological methods for the diagnosis of Neospora caninum infection in bovines. Vet Parasitol 2004; 120(1-2): 11-22. PMid:15019139. http://dx.doi.org/10.1016/j.vetpar.2003.12.010.
http://dx.doi.org/10.1016/j.vetpar.2003....
). A cow with a single or two positive ELISA results was considered as N. caninum infected.

DNA extraction and PCR

DNA extractions from WBC, and intrathoracic fluid, and tissues were performed by using the PureLink™ Genomic DNA Purification kit (Invitrogen) following the manufacture’s recommendations, and a negative control (water) was included in each DNA extraction. All PCR assays were done as previously described (MARQUES et al., 2011Marques FA, Headley AS, Figueredo-Pereira V, Taroda A, Barros LD, Cunha IA, et al. Neospora caninum: evaluation of vertical transmission in slaughtered beef cows (Bos indicus). Parasitol Res 2011; 108(4): 1015-1019. PMid:21063729. http://dx.doi.org/10.1007/s00436-010-2146-x.
http://dx.doi.org/10.1007/s00436-010-214...
). N. caninum DNA was amplified by using the Np21+ and Np6+ primers (MULLER et al., 2001Müller N, Sager H, Hemphill A, Mehlhorn H, Heydorn AO, Gottstein B. Comparative molecular investigation of Nc5-PCR amplicons from Neospora caninum NC-1 and Hammondia heydorni-Berlin-1996. Parasitol Res 2001; 87(10): 883-885. PMid:11688897. http://dx.doi.org/10.1007/s004360100463.
http://dx.doi.org/10.1007/s004360100463...
) in a PCR assay performed in a mixture containing 5 μl of extracted DNA with 20 μl (final volume of 25 μl) of mixture of 1.0 mM of each primer, 100mM dNTP (Invitrogen, Life Technologies. USA), 60mM Tris–HCl (pH 9.0), 15mM (NH4)2SO4, 1.5 mM MgCl2 and 0.5U Taq DNA polymerase (Invitrogen, Life Technologies. USA). Amplification of protozoan DNA was done over 35 cycles in a PTC-100 thermocycler (MJ-Research), using the following cycling conditions for PCR: 5 min at 94 °C, followed by 35 cycles for 30 s at 94 °C, 30 s at 65 °C and 60 s at 72 °C. Cycle 35 was followed by a final extension of 7 min at 72 °C. Aliquots of each PCR product were electrophoresed on 2% agarose gels. Tachyzoites of the NC-1 strain (106/ml) were diluted in TE buffer, the DNA extracted, and used as positive control. The negative control consisted of water samples without N. caninum; positive and negative controls were included in each assay.

Pathological evaluation

Cerebrum tissue fragments were collected from all fetuses, and fixed by immersion in 10% buffered formalin solution, routinely processed for histopathological evaluation, and then evaluated for the presence of pathological alterations.

Immunohistochemistry

Cerebrum, myocardium, lung and liver tissue fragments from fetuses were placed into 10% formal saline solution and fixed for five days. The fixed tissues were then processed by standard procedures to paraffin-wax blocks, after which slides were produced for hematoxylin and eosin staining (MALEY et al., 2003Maley SW, Buxton D, Rae AG, Wright SE, Schock A, Bartley PM, et al. The pathogenesis of neosporosis in pregnant cattle: inoculation at mid-gestation. J Comp Pathol 2003; 129(2-3): 186-195. PMid:12921725. http://dx.doi.org/10.1016/S0021-9975(03)00032-X.
http://dx.doi.org/10.1016/S0021-9975(03)...
). The immunohistochemistry technique was done as previously described (MALEY et al., 2003Maley SW, Buxton D, Rae AG, Wright SE, Schock A, Bartley PM, et al. The pathogenesis of neosporosis in pregnant cattle: inoculation at mid-gestation. J Comp Pathol 2003; 129(2-3): 186-195. PMid:12921725. http://dx.doi.org/10.1016/S0021-9975(03)00032-X.
http://dx.doi.org/10.1016/S0021-9975(03)...
). Briefly, paraffin-wax sections were cut and mounted on polylysinated glass slides (Superfrost® Plus; Menzel-Gläser) and dried overnight at 37°C. Glass slides were dewaxed and rehydrated. Endogenous peroxidase was blocked by incubating with 4% hydrogen peroxide in methanol for 30 min at room temperature (RT). Non-specific labeling was reduced by incubation with 25% normal goat serum in TBS for 30 min at RT. The tissue sections were then incubated overnight at 4°C with polyclonal primary antibodies produced against N. caninum tachyzoites (VMRD Inc, Washington, USA). After washes with TBS, anti-rabbit IgG polymers (Dako EnVision®) were employed as secondary antibodies. The reaction was revealed after incubation with DAB chromogen (Dako EnVision®) for 8 min. Slides were then washed with distilled water and counterstained using Mayer’s Hematoxylin for 30 seconds before being dehydrated and mounted.

Statistical analysis

Variables were analyzed by the Chi-square test (χ2) corrected by the Yates, Fisher Exact Test using the Epi 6 program (CDC. 6.04b version). The association among variables and occurrence of seropositivity was estimated from values obtained by the odds ratio (OR) with a confidence interval of 95%. A p-value of ≤ 0.05 was considered as significant in both tests.

Results

The results for N. caninum from cows and aborted fetuses are shown in Table 1. From the 41 dairy cows that aborted 21 (51.2%) were seropositive for N. caninum. The average S/P value of cows by ELISA, in the first bleeding, was 1.12±0.98. The average gestational age of abortions was 6.77±1.16 months; 13 (34.2%) were aborted at 4-6 months of pregnancy and 25 (65.8%) at 7-9 months. At second revisited six animals were slaughtered and consequently could not be sampled, thus, 35 paired serum samples were obtained. The positivity at the second collection was 48.5% (17/35) with an S/P average =1.01±0.91. The sample of one cow (N.10) was seropositive during the first reaction but negative at the second round of sampling, and thus considered as N. caninum infected. No blood samples derived from cows were positive by PCR.

Table 1
The outcome of Neospora caninum-induced infections in dairy cows (Bos taurus) and their aborted fetuses.

Three fetuses were mummified, preventing ELISA or PCR evaluations. Eight (26.7%) out of 30 fetal intrathoracic fluids were positive by ELISA, the average of fetal gestational age was 7.22±0.66 months, and the average of S/P for fetuses was S/P=0.56±1.04; six (35.3%) and four (23.5%) of these animals were positive by PCR and IHC, respectively (Table 1). A total of 14 (38.8%) and 9 (25%) tissue samples from 36 fetuses were positive by PCR and by IHC, respectively.

The most significant histopathological alterations observed are shown in Table 1. These consisted primarily of vascular alterations, and included hypertrophy of endothelial cells and congestion of blood vessels; intralesional cysts were not observed. The IHC test detected N. caninum antigens in four heart and six brain samples. There were no IHC positive results either in lung or liver.

Cows between 24-36 months of age had a protector factor of being serum positive [OR=0.00; (0.00<OR<0.31); p=0.0001] than animals > 36 months of age (Table 2). All cows aborted at more than four months of gestation, and there were no statistical differences (p=0.84). No significant differences (p=0.97) were observed when the breed (Holstein and Jersey) of the cows was evaluated.

Table 2
Association between the age of cows, gestational period, and breed with the presence of antibodies against Neospora caninum from dairy cows that aborted.

When we compared the positive maternal ELISA results with the results obtained by ELISA, PCR, and IHC from their fetuses we observed higher frequencies of having either serum (p=0.0002), PCR (OR=9.78; 1.63<OR<67.5; p=0.007) or IHC (OR=5.9; 0.85<OR<52; p=0.05) being positive (Table 3). All positive ELISA fetuses had positive ELISA cows.

Table 3
Results of ELISA from dams compared with ELISA, PCR, and IHC from fetuses.

Discussion

In the present study, from the 41 dairy cows that aborted, 51.2% were seropositive for N. caninum; comparatively lower seropositivity were reported for N. caninum in other studies, varying between 6.3 to 28.6% (MEERSCHMAN et al., 2002Meerschman F, Speybroeck N, Berkvens D, Rettigner C, Focant C, Leclipteux T, et al. Fetal infection with Neospora caninum in dairy and beef cattle in Belgium. Theriogenology 2002; 58(5): 933-945. PMid:12212893. http://dx.doi.org/10.1016/S0093-691X(02)00934-2.
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; KOIWAI et al., 2005Koiwai M, Hamaoka T, Haritani M, Shimizu S, Kimura K, Yamane I. Proportion of abortions due to neosporosis among dairy cattle in Japan. J Vet Med Sci 2005; 67(11): 1173-1175. PMid:16327231. http://dx.doi.org/10.1292/jvms.67.1173.
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; YILDIZ et al., 2009Yildiz K, Kul O, Babur C, Kilic S, Gazyagci AN, Celebi B, et al. Seroprevalence of Neospora caninum in dairy cattle ranches with high abortion rate: special emphasis to serologic co-existence with Toxoplasma gondii, Brucella abortus and Listeria monocytogenes. Vet Parasitol 2009; 164(2-4): 306-310. PMid:19592171. http://dx.doi.org/10.1016/j.vetpar.2009.06.004.
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). In this study, dams that were more than 36 months of age had a higher risk of being seropositive; similar findings were previously described (DUBEY et al., 2007Dubey JP, Schares G, Ortega-Mora LM. Epidemiology and control of neosporosis and Neospora caninum. Clin Microbiol Rev 2007; 20(2): 323-367. PMid:17428888. http://dx.doi.org/10.1128/CMR.00031-06.
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; HORNOK et al., 2006Hornok S, Edelhofer R, Hajtos I. Seroprevalence of neosporosis in beef and dairy cattle breeds in Northeast Hungary. Acta Vet Hung 2006; 54(4): 485-491. PMid:17278720. http://dx.doi.org/10.1556/AVet.54.2006.4.6.
http://dx.doi.org/10.1556/AVet.54.2006.4...
). It has been demonstrated that sero-prevalence might increase with the age and the number of gestations in beef and dairy cattle (DUBEY et al., 2007Dubey JP, Schares G, Ortega-Mora LM. Epidemiology and control of neosporosis and Neospora caninum. Clin Microbiol Rev 2007; 20(2): 323-367. PMid:17428888. http://dx.doi.org/10.1128/CMR.00031-06.
http://dx.doi.org/10.1128/CMR.00031-06...
; HORNOK et al., 2006Hornok S, Edelhofer R, Hajtos I. Seroprevalence of neosporosis in beef and dairy cattle breeds in Northeast Hungary. Acta Vet Hung 2006; 54(4): 485-491. PMid:17278720. http://dx.doi.org/10.1556/AVet.54.2006.4.6.
http://dx.doi.org/10.1556/AVet.54.2006.4...
), suggesting that horizontal transmission is of importance in cattle herds.

This study demonstrated that 26.7% (8/30) of the serum evaluated fetuses were positives to N. caninum antibodies; this results is more elevated, despite the use of different techniques, than that described in a similar study (SANTOS et al., 2005aSantos APME, Navarro IT, Bracarense APFRL, Freire RL, Marana ERM, Ogawa L, et al. Dairy cow abortion associated with Neospora caninum and other infectious agents. Arq Bras Med Vet Zootec 2005a; 57(4): 545-547. http://dx.doi.org/10.1590/S0102-09352005000400017.
http://dx.doi.org/10.1590/S0102-09352005...
), that used the IFA and obtained 11.7% (4/34) of seropositivity. Additionally, during this study all fetuses that were serum positive originated from dams that were also serum positive for N. caninum.

In the present study, there were three cows that had negative serology results for N. caninum but the fetuses of 3 were positive by PCR and one of their fetuses tested positive by IHC. Several factors can affect the PCR techniques; sensitivity, specificity, parasite detectability in the presence of host DNA and defective templates, mainly linked to quality of DNA extraction, additionally a false positive result due to contamination at nested-PCR is reported (MÜLLER et al., 2001Müller N, Sager H, Hemphill A, Mehlhorn H, Heydorn AO, Gottstein B. Comparative molecular investigation of Nc5-PCR amplicons from Neospora caninum NC-1 and Hammondia heydorni-Berlin-1996. Parasitol Res 2001; 87(10): 883-885. PMid:11688897. http://dx.doi.org/10.1007/s004360100463.
http://dx.doi.org/10.1007/s004360100463...
; MARQUES et al., 2011Marques FA, Headley AS, Figueredo-Pereira V, Taroda A, Barros LD, Cunha IA, et al. Neospora caninum: evaluation of vertical transmission in slaughtered beef cows (Bos indicus). Parasitol Res 2011; 108(4): 1015-1019. PMid:21063729. http://dx.doi.org/10.1007/s00436-010-2146-x.
http://dx.doi.org/10.1007/s00436-010-214...
). Fluctuating of N. caninum antibody levels in naturally infected cows was previously described (CARDOSO et al., 2012Cardoso JM, Amaku M, Araújo AJ, Gennari SM. A longitudinal study of Neospora caninum infection on three dairy farms in Brazil. Vet Parasitol 2012; 187(3-4): 553-557. PMid:22309800. http://dx.doi.org/10.1016/j.vetpar.2012.01.019.
http://dx.doi.org/10.1016/j.vetpar.2012....
; CONRAD et al., 1993Conrad PA, Sverlow K, Anderson M, Rowe J, BonDurant R, Tuter G, et al. Detection of serum antibody responses in cattle with natural or experimental Neospora infections. J Vet Diagn Invest 1993; 5(4): 572-578. PMid:8286457. http://dx.doi.org/10.1177/104063879300500412.
http://dx.doi.org/10.1177/10406387930050...
; DIJKSTRA et al., 2008Dijkstra T, Lam TJ, Bartels CJ, Eysker M, Wouda W. Natural postnatal Neospora caninum infection in cattle can persist and lead to endogenous transplacental infection. Vet Parasitol 2008; 152(3-4): 220-225. PMid:18280662. http://dx.doi.org/10.1016/j.vetpar.2007.12.034.
http://dx.doi.org/10.1016/j.vetpar.2007....
; KYAW et al., 2005Kyaw T, Suwimonteerabutr J, Virakul P, Lohachit C, Kalpravidh W. Seronegative conversion in four Neospora caninum-infected cows, with a low rate of transplacental transmission. Vet Parasitol 2005; 131(1-2): 145-150. PMid:15939537. http://dx.doi.org/10.1016/j.vetpar.2005.04.025.
http://dx.doi.org/10.1016/j.vetpar.2005....
; MARQUES et al., 2011Marques FA, Headley AS, Figueredo-Pereira V, Taroda A, Barros LD, Cunha IA, et al. Neospora caninum: evaluation of vertical transmission in slaughtered beef cows (Bos indicus). Parasitol Res 2011; 108(4): 1015-1019. PMid:21063729. http://dx.doi.org/10.1007/s00436-010-2146-x.
http://dx.doi.org/10.1007/s00436-010-214...
). The observation that some infected dams can exhibit negative antibody values during any gestational period, particularly Neospora at parturition or abortion was previously demonstrated (BENAVIDES et al., 2012Benavides J, Katzer F, Maley SW, Bartley PM, Canton G, Palarea-Albaladejo J, et al. High rate of transplacental infection and transmission of Neospora caninum following experimental challenge of cattle at day 210 of gestation. Vet Res 2012; 43(1): 83. PMid:23228067. http://dx.doi.org/10.1186/1297-9716-43-83.
http://dx.doi.org/10.1186/1297-9716-43-8...
; NOGAREDA et al., 2007Nogareda C, López-Gatius F, Santolaria P, García-Ispierto I, Bech-Sàbat G, Pabón M, et al. Dynamics of anti-Neospora caninum antibodies during gestation in chronically infected dairy cows. Vet Parasitol 2007; 148(3-4): 193-199. PMid:17643822. http://dx.doi.org/10.1016/j.vetpar.2007.06.032.
http://dx.doi.org/10.1016/j.vetpar.2007....
). It has been reported that 5% (8/170) (PARÉ et al., 1996Paré J, Thurmond MC, Hietala SK. Congenital Neospora caninum infection in dairy cattle and associated calfhood mortality. Can J Vet Res 1996; 60(2): 133-139. PMid:8785719.) and 3% (1/33) (MORE et al., 2009Moré G, Bacigalupe D, Basso W, Rambeaud M, Beltrame F, Ramirez B, et al. Frequency of horizontal and vertical transmission for Sarcocystis cruzi and Neospora caninum in dairy cattle. Vet Parasitol 2009; 160(1-2): 51-54. PMid:19070964. http://dx.doi.org/10.1016/j.vetpar.2008.10.081.
http://dx.doi.org/10.1016/j.vetpar.2008....
) of seronegative cows gave birth to seropositive calves. This shows that caution must be taken in the interpretation of serologic results if they are to be used in control strategies for bovine neosporosis (CONRAD et al., 1993Conrad PA, Sverlow K, Anderson M, Rowe J, BonDurant R, Tuter G, et al. Detection of serum antibody responses in cattle with natural or experimental Neospora infections. J Vet Diagn Invest 1993; 5(4): 572-578. PMid:8286457. http://dx.doi.org/10.1177/104063879300500412.
http://dx.doi.org/10.1177/10406387930050...
).

It has been demonstrated that abortions caused by N. caninum may occur from 3 months of gestation to term (DUBEY & LINDSAY, 1996Dubey JP, Lindsay DS. A review of Neospora caninum and neosporosis. Vet Parasitol 1996; 67(1-2): 1-59. PMid:9011014. http://dx.doi.org/10.1016/S0304-4017(96)01035-7.
http://dx.doi.org/10.1016/S0304-4017(96)...
). The average (±SD) gestational age of abortions that was suggestive for neosporosis in this study was 7.22±0.66 months, ranging from 6 to 8 months; similar results have been described (MEERSCHMAN et al., 2002Meerschman F, Speybroeck N, Berkvens D, Rettigner C, Focant C, Leclipteux T, et al. Fetal infection with Neospora caninum in dairy and beef cattle in Belgium. Theriogenology 2002; 58(5): 933-945. PMid:12212893. http://dx.doi.org/10.1016/S0093-691X(02)00934-2.
http://dx.doi.org/10.1016/S0093-691X(02)...
; SAGER et al., 2001Sager H, Fischer I, Furrer K, Strasser M, Waldvogel A, Boerlin P, et al. A Swiss case-control study to assess Neospora caninum-associated bovine abortions by PCR, histopathology and serology. Vet Parasitol 2001; 102(1-2): 1-15. PMid:11705647. http://dx.doi.org/10.1016/S0304-4017(01)00524-6.
http://dx.doi.org/10.1016/S0304-4017(01)...
).

Although the histopathological alterations seen within the brain are non-specific, positive IHC staining for N. caninum was observed either in the cerebrum or in the myocardium of six (60%) fetuses that also had non-specific histopathological changes. In contrast, typical N. caninum-induced lesions were reported within the brain of fetuses that were experimentally infected (BENAVIDES et al., 2012Benavides J, Katzer F, Maley SW, Bartley PM, Canton G, Palarea-Albaladejo J, et al. High rate of transplacental infection and transmission of Neospora caninum following experimental challenge of cattle at day 210 of gestation. Vet Res 2012; 43(1): 83. PMid:23228067. http://dx.doi.org/10.1186/1297-9716-43-83.
http://dx.doi.org/10.1186/1297-9716-43-8...
). Additionally, N. caninum-induced necrosis was observed within the skeletal muscles of aborted fetuses whose dams were experimentally infected, but without similar lesions present within the brain, lung, kidneys, and myocardium (McCANN et al., 2007McCann CM, McAllister MM, Gondim LF, Smith RF, Cripps PJ, Kipar A, et al. Neospora caninum in cattle: experimental infection with oocysts can result in exogenous transplacental infection, but not endogenous transplacental infection in the subsequent pregnancy. Int J Parasitol 2007; 37(14): 1631-1639. PMid:17624353. http://dx.doi.org/10.1016/j.ijpara.2007.05.012.
http://dx.doi.org/10.1016/j.ijpara.2007....
). Nevertheless, these results confirm the superiority of IHC relative to histopathology for the identification of N. caninum within tissue fragments.

A combination of maternal ELISA and fetal ELISA, PCR and IHC gave a better indication of transmission of the parasite to the fetus than maternal ELISA results alone. The PCR assay is considered as a valuable technique for the diagnosis of N. caninum (SERRANO-MARTINEZ et al., 2007Serrano-Martínez E, Ferre I, Osoro K, Aduriz G, Mota RA, Martinez A, et al. Intrauterine Neospora caninum inoculation of heifers and cows using contaminated semen with different numbers of tachyzoites. Theriogenology 2007; 67(4): 729-737. PMid:17126895. http://dx.doi.org/10.1016/j.theriogenology.2006.10.004.
http://dx.doi.org/10.1016/j.theriogenolo...
), and the results from this study have demonstrated that 38.8% (14/36) of the aborted fetuses were positive. Similar findings were described by nested PCR where 80% and 57.7% (MEDINA et al., 2006Medina L, Cruz-Vázquez C, Quezada T, Morales E, García-Vázquez Z. Survey of Neospora caninum infection by nested PCR in aborted fetuses from dairy farms in Aguascalientes, Mexico. Vet Parasitol 2006; 136(3-4): 187-191. PMid:16332413. http://dx.doi.org/10.1016/j.vetpar.2005.11.003.
http://dx.doi.org/10.1016/j.vetpar.2005....
; YAO et al., 2009Yao L, Yang N, Liu Q, Wang M, Zhang W, Qian WF, et al. Detection of Neospora caninum in aborted bovine fetuses and dam blood samples by nested PCR and ELISA and seroprevalence in Beijing and Tianjin, China. Parasitology 2009; 136(11): 1251-1256. PMid:19660160. http://dx.doi.org/10.1017/S0031182009990813.
http://dx.doi.org/10.1017/S0031182009990...
) of aborted fetuses were positive for N. caninum, in Mexico and China, respectively. However, other studies (PEREIRA-BUENO et al., 2003Pereira-Bueno J, Quintanilla-Gozalo A, Pérez-Pérez V, Espi-Felgueroso A, Alvarez-GarcÍa G, Collantes-Fernández E, et al. Evaluation by different diagnostic techniques of bovine abortion associated with Neospora caninum in Spain. Vet Parasitol 2003; 111(2-3): 143-152. PMid:12531290. http://dx.doi.org/10.1016/S0304-4017(02)00361-8.
http://dx.doi.org/10.1016/S0304-4017(02)...
; RAZMI et al., 2006Razmi GR, Mohammadi GR, Garrosi T, Farzaneh N, Fallah AH, Maleki M. Seroepidemiology of Neospora caninum infection in dairy cattle herds in Mashhad area, Iran. Vet Parasitol 2006; 135(2): 187-189. PMid:16289861. http://dx.doi.org/10.1016/j.vetpar.2005.09.004.
http://dx.doi.org/10.1016/j.vetpar.2005....
, 2010Razmi GR, Zarea H, Naseri Z. A survey of Neospora caninum-associated bovine abortion in large dairy farms of Mashhad, Iran. Parasitol Res 2010; 106(6): 1419-1423. PMid:20352453. http://dx.doi.org/10.1007/s00436-010-1820-3.
http://dx.doi.org/10.1007/s00436-010-182...
; SAGER et al., 2001Sager H, Fischer I, Furrer K, Strasser M, Waldvogel A, Boerlin P, et al. A Swiss case-control study to assess Neospora caninum-associated bovine abortions by PCR, histopathology and serology. Vet Parasitol 2001; 102(1-2): 1-15. PMid:11705647. http://dx.doi.org/10.1016/S0304-4017(01)00524-6.
http://dx.doi.org/10.1016/S0304-4017(01)...
) have described values that ranged from 11.9 to 33%. Thus, the results of this investigation are in agreement with the diagnosis of N. caninum-associated abortions in dairy cattle worldwide, where it was demonstrated that 12 to 45% of aborted fetuses are infected by this protozoan parasite (DUBEY, 2005Dubey JP. Neosporosis in cattle. Vet Clin North Am Food Anim Pract 2005; 21(2): 473-483. PMid:15955441. http://dx.doi.org/10.1016/j.cvfa.2005.03.004.
http://dx.doi.org/10.1016/j.cvfa.2005.03...
).

In summary, the present study observed a high frequency of N. caninum in abortions from dairy cows from southern Brazil, with a higher N. caninum prevalence found in cows that were older than 36 months. In addition, serology, PCR, and IHC should be used in combination for better diagnosis of neosporosis in cattle.

Acknowledgements

The authors would like to thank Coordenação de Aperfeicoamento de Pessoal de Nivel Superior (CAPES AUXPE-1345/11), and Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq 304083/2015-1). JL Garcia and S. A. Headley are recipient of CNPq fellowships. EA Innes, F Katzer and F. Chianini were supported by the Scottish Government, and The Rural and Environment Science and Analytical Services.

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Publication Dates

  • Publication in this collection
    Jul-Sep 2017

History

  • Received
    29 Jan 2017
  • Accepted
    21 Aug 2017
Colégio Brasileiro de Parasitologia Veterinária FCAV/UNESP - Departamento de Patologia Veterinária, Via de acesso Prof. Paulo Donato Castellane s/n, Zona Rural, , 14884-900 Jaboticabal - SP, Brasil, Fone: (16) 3209-7100 RAMAL 7934 - Jaboticabal - SP - Brazil
E-mail: cbpv_rbpv.fcav@unesp.br