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On-line version ISSN 1678-4162
Arq. Bras. Med. Vet. Zootec. vol.55 no.3 Belo Horizonte June 2003
Prevalence of Hepatozoon spp. (Apicomplexa, Hepatozoidae) among recently captured Brazilian snakes
Prevalência de Hepatozoon spp. (Apicomplexa, Hepatozoidae) em serpentes recém-capturadas no Brasil
L.H. O'DwyerI; T.C. MoçoI; T.H. BarrellaII; F.C. VilelaII; R.J. SilvaI
IDepartamento de Parasitologia, Instituto de Biociências Universidade Estadual Paulista (UNESP) 18618-000 - Botucatu, SP
IICentro de Estudos de Venenos e Animais Peçonhentos (CEVAP) da UNESP
The goal of this study was to determine the prevalence of Hepatozoon spp. infection in recently captured snakes from Botucatu, São Paulo State, Brazil. Blood was collected from all snakes by ventral tail venipuncture. Blood smears were air dried, fixed with methanol, and stained with 10% Giemsa solution. The slides were microscopically examined for detection of hemoparasites by light microscopy at 250x magnification. A total of 238 snakes from 23 species were examined, of which 135 (56.7%) were venomous and 103 (43.3%) non-venomous snakes. The more numerous venomous species sampled were Crotalus durissus terrificus (n=108) and Bothrops jararaca (n=17) and non-venomous snakes were Oxyrhopus guibei (n=35), Boa constrictor amarali (n=18), and Waglerophis merremi (n=13). Hepatozoon spp. infection was detected in 39 (16.4%) snakes. The prevalence in venomous and non-venomous snakes was 20.0% and 11.7%, respectively. The highest prevalences observed were 38.9% for Boa constrictor amarali, 35.3% for Bothrops jararaca, and 19.4% for Crotalus durissus terrificus.
Key words: snake, Hepatozoon, prevalence, infection
O presente estudo teve como objetivo determinar a prevalência da infecção por Hepatozoon spp. em serpentes recém-capturadas da região de Botucatu, São Paulo. O sangue foi coletado de todas as serpentes por punção da veia caudal. Os esfregaços foram secos ao ar, fixados com metanol e corados com solução de Giemsa a 10%. Examinaram-se 238 serpentes pertencentes a 23 espécies, das quais 135 (56,7%) eram venenosas e 103 (43,3%) não venenosas. As espécies venenosas mais representativas foram Crotalus durissus terrificus (n=108) e Bothrops jararaca (n=17) e as não venenosas foram Oxyrhopus guibei (n=35), Boa constrictor amarali (n=18) e Waglerophis merremi (n=13). A infecção por Hepatozoon spp. foi detectada em 39 (16,4%) serpentes. As prevalências em serpentes venenosas e não venenosas foram 20,0% e 11,7%, respectivamente. As maiores prevalências foram 38,9% para Boa constrictor amarali, 35,3% para Bothrops jararaca e 19,4% para Crotalus durissus terrificus.
Palavras-chave: serpente, Hepatozoon, prevalência, infecção
Members of the genera Hepatozoon (Hepatozoidae) are the most common group of intracellular protozoa found in snakes (Telford, 1984). The life cycle of species within this genus is characterized by sporogonic development in a hematophagous arthropod that results in the formation of large oocysts, with hundreds of sporocysts containing sporozoites. Merogonic and gamontogonic development occurs in the internal organs of a vertebrate host after ingestion of an infected definitive host or an intermediate vertebrate host (Smith, 1996).
Many arthropods (mosquitoes, triatominae bugs, phlebotominae sand flies, tsetse flies, mites and ixodid ticks) have been shown to be capable vectors of Hepatozoon spp. (Wozniak, Telford Jr., 1991). Particularly, mosquitoes have been experimentally infected with Hepatozoon sp. of snakes (Pessoa et al., 1971a,b; Pessoa, De Biasi, 1973; Pessoa et al., 1974b; Bashtar et al., 1991). However, mosquitoes are not normally eaten by snakes and therefore direct transmission from mosquitoes to snakes seems unlikely in nature (Smith, 1996). Thus, snakes can be infected by ingestion of an infected intermediate vertebrate host or other arthropod vectors.
These hemoparasites are apparently well adapted since they cause little or no pathological changes in their natural hosts (Telford, 1984). The maintenance of reptile species in captivity sometimes provides optimal conditions for transmission of these parasites (Hull, Camin, 1960). In the semi-extensive breeding system, a great number of snakes were kept close together and the environment favor proliferation of arthropods that can act as vectors. The infection can cause clinically significant inflammatory disease in non-host species (Wozniak, Telford, 1991), and hemolytic anemia may occur in natural hosts upon heavy infection (Mader, 1996). Therefore, the prevalence of Hepatozoon spp. should be established and reptiles should be examined prior to admission into zoos. There is no information on chemotherapy for Hepatozoon (Mader, 1996).
There are few studies on the prevalence of Hepatoozon spp. from snakes. The available studies were performed in the 1960's and 1970's. Hull and Camin (1960) examined 600 captive snakes from United States zoos and found that 154 (30.8%) were infected with Hepatozoon spp. In Brazil, snake hemoparasites have been characterized (Pessoa, 1967a,b,c,d,e), however, there is only one prevalence study carried out by Pessoa et al. (1974a), in which the authors found a 17.1% of prevalence among a total of 2128 snakes, but the authors did not mention if the analysis was performed on recently captured or captive snakes.
The goal of this study was to investigate the prevalence of Hepatozoon spp. among recently captured Brazilian snakes.
MATERIAL AND METHODS
Snakes recently captured in São Paulo State, Brazil, were donated to the Center for Study of Venoms and Venomous Animals at São Paulo State University, in Botucatu, and were examined from two to five days after the capture. All specimens were identified and had their sex, weight and length determined. The geographic origins and dates of collection were also recorded. Blood was collected from all snakes by ventral tail venipuncture. Thin blood smears were prepared immediately upon collection, air dried, fixed with methanol for three minutes, and stained with 10% Giemsa solution for 30 minutes. The slides were examined for detection of hemoparasites by light microscopy at 250x magnification.
A total of 238 snakes were examined, of which 135 (56.7%) were venomous and 103 (43.3%) non-venomous. Of these, 55.5% were females and 36.5% were males, and in 8.0% of the snakes sex could not be determined. The species examined are listed in Table 1. The more representative venomous species were Crotalus durissus terrificus (n=108) and Bothrops jararaca (n=17) and non-venomous snakes were Oxyrhopus guibei (n=35), Boa constrictor amarali (n=18) and Waglerophis merremi (n=13). The snakes studied came from 35 municipalities in São Paulo State, Brazil (Fig. 1), but most of them (39.9%) from Botucatu.
Towns where infected and non-infected snakes were found (black stars): 1) Anhembi, 2) Bocaína, 3) Botucatu, 4) Conchas, 5) Dois Córregos, 6) Itatinga, 7) Laranjal Paulista, 8) Piapara, 9) Piracicaba, 10) Salto, and 11) Votuporanga. Towns where only non-infected snakes were found (gray square): 1) Águas de Lindóia, 2) Avaré, 3) Bauru, 4) Bofete, 5) Cabreúva, 6) Cerqueira Cesar, 7) Fartura, 8) Ibitinga, 9) Itapeva, 10) Itaporanga, 11) Jau, 12) Lucélia, 13) Mineiros do Tietê, 14) Paranapanema, 15) Pardinho, 16) Pereiras, 17) Piraju, 18) Pirambóia, 19) Porto Primavera, 20) Pratânea, 21) Santa Maria da Serra, 22) São Manuel, 23) São Pedro, and 24) Ubatuba.
Hepatozoon spp. infection (Fig. 2) was detected in 39 (16.4%) snakes. The prevalence in venomous and non-venomous snakes was 20.0% and 11.7%, respectively. The highest prevalences observed were 38.9% for Boa constrictor amarali, 35.3% for Bothrops jararaca, and 19.4% for Crotalus durissus terrificus.
A similar prevalence of infection by Hepatozoon spp. was observed in females (15.9%) and males (17.2%). Analysis of prevalence in the species with a representative number of snakes indicated that the prevalence among males and females was similar for the venomous snakes, whereas it was higher among females of non-venomous snakes (Fig. 3). Regarding the origin of infected snakes, the prevalence was higher in Salto (75.0%), Anhembi (44.4%) and Botucatu (21.1%) (Fig. 1).
In this study a 16.4% prevalence of Hepatozoon spp. infection was found. This result is similar to that previously reported by Pessoa et al. (1974a), who found a 17.1% prevalence among a total of 2128 Brazilian snakes, but it is different from the report by Hull and Camin (1960), who detected a 30.8% prevalence among a total of 600 captive snakes from United States zoos. The difference between the prevalences observed in Brazil and in the United States may be related to the ecological conditions of each country as well as the abundance of vectors, host snakes, and climatic characteristics.
Although the total prevalence found in this study was similar to that reported by Pessoa et al. (1974a), when the infection was analyzed according to species significant differences were observed. Prevalences for Boa constrictor amarali, Bothrops jararaca and Crotalus durissus terificus were 38.9%, 35.3%, and 19.4%, respectively, as opposed to 62.0%, 24.0%, and 11.0%, respectively, in the study by Pessoa et al. (1974a). Since these investigators did not report the time of capture, the higher prevalence observed in Boa constrictor amaralis may be due to the system of animal maintenance, which may favor transmission of the parasite in captivity. Considering that all those species are ovoviviparous (Silva, 2000) and that the possibility of congenital transmission of the parasite exists (De Biasi et al., 1971; 1972), a higher rate of infestation in animals born in captivity may be related to these factors.
In regard to sex, similar prevalences were observed between males and females. However, for the species Boa constrictor amarali, the infection was more frequent among females (57.1% versus 14.3%), although the same number of males and females were examined.
Studies on the prevalence of Hepatozoon spp. infection in snakes are scarce. Evaluation of the infection under natural conditions in Brazil was not available. Such information is important when these animals are chosen for captive breeding. Future studies will be carried out to determine the most common species of the genus Hepatozoon infecting Brazilian snakes.
This investigation received financial support from Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP). T.C.M. was supported by the FAPESP.
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Recebido para publicação em 14 de agosto de 2002
Recebido para publicação, após modificações, em 9 de dezembro de 2002