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Revista da Sociedade Brasileira de Medicina Tropical

Print version ISSN 0037-8682

Rev. Soc. Bras. Med. Trop. vol.47 no.3 Uberaba May/June 2014

http://dx.doi.org/10.1590/0037-8682-0169-2013 

Short Communications

Hematologic profile of hematophagous Desmodus rotundus bats before and after experimental infection with rabies virus

Marilene Fernandes de Almeida[1] 

José Trezza-Netto[1] 

Caroline Cotrin Aires[2] 

Rodrigo Fernandes de Barros[3] 

Adriana Ruckert da Rosa[1] 

Eduardo Massad[4]  [5] 

[1]Centro de Controle de Zoonoses, Coordenação de Vigilância em Saúde, Prefeitura da Cidade de São Paulo, São Paulo, SP

[2]Supervisão de Vigilância em Saúde, Secretaria Municipal de Saúde, Prefeitura da Cidade de São Paulo, São Paulo, SP

[3]Universidade Nove de Julho, São Paulo, SP

[4]Faculdade de Medicina, Universidade de São Paulo, São Paulo, SP

[5]Department of Infectious and Tropical Diseases (Hon. Prof.), London School of Hygiene & Tropical Medicine, London, UK

ABSTRACT

Introduction

Hematophagous Desmodus rotundus bats play an important role in the rabies lifecycle. This study describes the hematological profile of these bats before and after experimental infection with rabies virus.

Methods

Cells counts were performed in a Neubauer chamber.

Results

The average values of erythrocytes and leucocytes counts in blood before experimental infections were 9.97 × 106mm3 and 4.80 × 103mm3, respectively. Neutrophils represented 69.9% of white blood cells and the lymphocytes represented 26.9%. Following the experimental infections, the average numbers of erythrocytes and leucocytes was 9.43 × 106mm3 and 3.98 × 103mm3, respectively. Neutrophils represented 40% of white blood cells and the lymphocytes represented 59%.

Conclusions

The hematological profile given in this study can serve as reference values for D. rotundus bats.

Key words: Bats; Hematology; Rabies

Among the 1,198 species of bats identified worldwide, only three species feed exclusively on blood, namely, the common vampire bat (Desmodus rotundus), the hairy-legged vampire bat (Diphylla ecaudata), and the white-winged vampire bat (Diaemus youngi). D. rotundus is the most common hematophagous bat, is found from Mexico to South America, and feeds on the blood of mammals, while the other two species use avian blood as a source of food1.

Because of its food preference, the D. rotundus bat is involved in the rabies cycle and is responsible for significant losses of livestock2. However, the therapeutic proprieties of the anticoagulant in their saliva and its orientation system make them the subject of many investigations3,4.

In this study, we examined the hematological profiles of D. rotundus bats before and after experimental infection with rabies virus in order to establish reference values for this species.

Bats were anesthetized with ketamine hydrochloride (Ketamina®) by injection into the pectoral muscle, considering the weight and volume (0.1ml/10g of body weight). Ninety-six blood samples were collected by intracardiac puncture using surface-heparinized 1ml syringes. Sixty-eight of the blood samples were collected before the experimental infection, and 28 were collected on day 33 following the experimental infection. Blood was taken from bats surviving rabies infection, clarifying the difference between the numbers in the samples.

The bats were euthanized in a CO2 chamber following blood collection. All procedures were designed to avoid animal suffering, and this research was approved by the Ethics Committee of São Paulo University. The capture of bats was authorized by a Brazilian institution responsible for wild animal care (Instituto Brasileiro do Meio Ambiente; license nr. 107/00).

One hundred ninety-five bats were maintained in captivity in biosafety cages specially designed for rabies experimentation5. The virus strain used for experimental infection was isolated from a naturally infected D. rotundus bat. The dose used was 105 MICLD50 (Mouse Intracerebral Lethal Dose), which was previously tested in studies of on rabies experimental infection6.

Before counting, red blood cells were first diluted 1:400 in 0.85% sodium chloride solution and white blood cells were diluted 1:5 in Turk solution. Blood cell impressions in slides were stained using Leishman staining. Cell counts were performed in a Neubauer chamber.

Before the rabies experimental infection, the average red blood cell was 9.97 × 106/mm3 (± 1.83 × 106/mm3) and average white blood cell was 4.80 × 103/mm3 (± 2.09 × 103/mm3). The neutrophils represented an average of 69.9% of blood cells, while lymphocytes represented 26.9%. After the experimental infection, the average of red blood cells was 9.43 × 106/mm3 (± 3.05 × 106/mm3), and that of white blood cells was 3.98 × 103/mm3 (± 2.21 × 103/mm3). Neutrophils represented an average of 40% of white blood cells and lymphocytes represented 59%.

We observed that the blood of hematophagous D. rotundus bats contains on average, 2-fold more red blood cells than found in human blood. In addition, the bat erythrocytes are smaller than those of humans, which was also observed by Sealander7 in relation to others small mammals. The reduced size of red blood cells in D. rotundus bats improves oxygen binding and, thus, enhances their ability to transport oxygen. Due to the small size and large number of red cells, the total surface area available for oxygenation is increased8. Besides their ability to fly, bats have also developed a highly specialized circulatory system to meet the needs of flight.

The number of erythrocytes observed in our study (Table 1) with D. rotundus bats is very similar to values reported previously913. High erythrocyte counts were also observed in studies with other bat species. Neuweiler8 showed values of erythrocytes varying between 9.3 × 106/mm3 and 15.4 × 106/mm3 in 15 species of bats. Baptista and Esberard12 showed average values of 8.04 × 106 erythrocytes/mm3 in four species of frugivorous bats belonging to the Artibeus genus. Similar results (8.9-10.1 × 106/mm3) were reported by Ratnasooriya14 for three species of bats from Sri Lanka.

TABLE 1 - Hematological profile of hematophagous bat Desmodus rotundus

White cells Neu Lin Eo Mo Ba Red cells Reference Cell counting method
4,808 x 103/mm3 69.9 26.9 0.0 2.7 0.5 9.97 x 106/mm3 This study Neubauer
8,412.5 x 103/mm3 84.5 11.3 0.75 3.0 0.0 8.56 x 106/mm3 9 Neubauer
11.2 x 103/mm3 72.0 20.0 1.0 4.4 0.25 9.5 x 106/mm3 10 automatic counter
12.06 x 103/mm3 77.3 15.0 0.8 3.67 0.07 9.18 x 106/mm3 11 automatic counter/Neubauer
3.67 x 103/mm3 37.3 44.2 0.75 8.9 0.23 10.71 x 106/mm3 12 not cited
11.09 x 103/mm3 78.1 10.6 0.0 8.1 3.2 9.021 x 106/mm3 8 automatic counter

Neu: neutrophils; Lin: lymphocytes; Eo: eosinophils; Mo: monocytes; Ba: basophils.

Hematological values for white blood cell counts have shown contradictory results. The number of white blood cells obtained in this study with D. rotundus bats was discordant with those reported by Almeida et al.9, Santos et al.10, Vilar et al.11, Baptista12 and was concordant with those reported by Krutzsch and Winsatt13. However, in studies performed by Almeida et al.9, Santos et al.10, and Vilar et al.12, leucograms showed high standard deviations (approximately 3.0 × 106/mm3 to 6.0 × 106/mm3).

In relation to the results for differential white blood cell counts, few basophils and monocytes were evident in the blood smears, while eosinophils were not observed. The proportion of neutrophils to lymphocytes was 7: 3, which is similar to those values reported by Santos et al.10, Vilar et al.11, and Baptista and Esbérard12.

As expected after a viral infection, there was a significant increase of lymphocytes and the proportion of neutrophils to lymphocytes changed from 7: 3 to 4: 6. In differential white blood cell counts, few basophils and monocytes were observed in blood smears, and eosinophils were not observed. No change in erythrocyte profiles was observed following experimental infection.

In conclusion, the values of erythrocytes observed in D. rotundus bats are in accord with several studies and may serve as reference values for this species, even considering the differences among methods of analysis used by each author. However, regarding leucocytes, more studies should be undertaken to better understand the wide variations in leucocyte counts observed in this species and to determine whether these differences are related to age, sex, size, or the reproductive state of bats, as observed by Ratnasooriya14 and Valdivieso and Tamsitt15 for other bats species.

REFERENCES

1. Reis NR, Shibatta AO, Peracchi AL, Pedro WA, Lima IP. Sobre os Morcegos Brasileiros. In: Reis NR, Peracchi AL, Pedro WA, Lima IP, editors. Morcegos do Brasil. Londrina; 2007. p. 17-25. [ Links ]

2. Pan-American Health Organization. Sistema de Informação Epidemiológica. Históricos Anuais. 2011. [Cited 2014, June 10]. Available from http://siepi.panaftosa.org.br/anuais.aspx [ Links ]

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4. Schnitzler HU, Moss CF, Denzinger A. From spatial orientation to food acquisition in echolocating bats. Trends Ecol Evol 2003; 18:386-394. [ Links ]

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6. Almeida MF, Martorelli LFA, Aires CC, Sallum PC, Durigon EL, Massad E. Experimental rabies infection in hematophagous bats Desmodus rotundus. Epidemiol Infec 2005; 133:523-527. [ Links ]

7. Sealander JA. The influence of body size, season, sex, age and other factors upon some blood parameters in small mammals source. J Mammal 1964; 45:598-616. [ Links ]

8. Neuweiler G. The biology of bats. Oxford, UK: Oxford University Press; 2000. [ Links ]

9. Almeida BFM, Barbosa TS, Ciarlini LSRP, Pedro WA, Beluccio ML, Queiroz LH, et al. Valores hematológicos de morcegos hematófagos Desmodus rotundus (E. Geoffroy, 1810) mantidos em cativeiro. Chiroptera Neotropical 2010; 16:780-785. [ Links ]

10. Santos AP, Mottin VD, Aita RS, Franciscatto C, Lopes STA, Franco WS, et al. Valores hematológicos e bioquímicos de morcegos hematófagos (Desmodus rotundus rotundus) no sul do Brasil. Acta Scientiae Veterinariae 2007; 35:55-58. [ Links ]

11. Vilar TD, Volino Vaz FM, Gitti CB, Cordeiro AV, Lobo R, Fonseca URC, et al. Hematologic values of Desmodus rotundus (Geoffroy, 1890) in Rio de Janeiro. Rev Univ Rural 2005; 25:57-58. [ Links ]

12. Baptista M, Esbérard C. Valores Hematológicos de Artibeus sp e Desmodus rotundus (Mammalia, Chiroptera). Rev Cient Inst Pesq Gonzaga da Gama Filho 1997; 3:11-22. [ Links ]

13. Krutzsch PH, Wimsatt WA. Some normal values of peripheral blood in the vampire bat. J Mammal 1963; 44:547-559. [ Links ]

14. Ratnasooriya WD, Udagama-Randeniya PV, Yapa WB, Digana PMCB, Dharmasini MG. Haematological parameters of three species of wild-caught microchiropteran bats, Miniopterus schreibersii, Taphozous melanopogon and Hipposideros lankadiva in Sri Lanka. J Sci Univ Kelaniya 2005; 2:27-40. [ Links ]

15. Valdivieso D, Tamsitt JR. Hematological data from tropical American bats. Can J of Zool 1971; 49:31-36. [ Links ]

Received: October 22, 2013; Accepted: February 14, 2014

Address to: Dra Marilene Fernandes de Almeida. CCZ/CVS/Prefeitura da Cidade de São Paulo. Rua Santa Eulália 86, Santana, 02031-020 São Paulo, SP, Brasil. Phone: 55 11 3397-8948; Fax: 55 11 2251-2249. e-mail: lenefalmeida@hotmail.com

CONFLICT OF INTEREST The authors declare that there is no conflict of interest.

Creative Commons License This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.