Megid,J*.; Almeida,M.F. ;Albas,A.
*Faculty of Veterinary Medicine- Dept. Veterinary Hygiene and Public Health
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This report describes the presence of rabies neutralizing antibodies in wild deer (Blastocerus dichotomus) from the western region of São Paulo State-Brazil .This suggests a low level rabies virus infection in the cervids, possibly due to natural transmission from infected bats in a rabies endemic region.
Rabies virus neutralizing antibodies
have been recorded previously in unvaccinated wild animals located in rabies
endemic areas (Constantine,1967; Lord et.al,1975; Carey & McLean,1983; Rosette
& Gunson,1984) . Affected species have included carnivores like foxes and
skunks (Lord et. al,1975; Rosette & Gunson,1984 ) , bats( Lord et. Al,1975)
and cattle (Lord et. Al,1975). The presence of seropositive wild species has
suggested not only a low viral titer infection in affected animals, but also
that they may play a role in the maintenance of latent rabies virus infection
(Carey & McLean,1983) .This report describes the presence of rabies serum
neutralizing antibodies in wild deer (Blastocerus dichotomus), from the western
region of São Paulo State,Brazil, a rabies endemic area.
Eight-two wild deer (B. dichotomus) were captured, examined clinically, and translocated to new areas. Serum from each deer was analysed for the presence of rabies neutralizing antibodies using established methods (Favoretto et al.,1993). All deer were clinically normal when captured. Rabies titers greater than 0.5 IU were observed in 11 animals (13,4%). Seven of these (8,5%) had titers greater than 1.0 IU and 4 (4,87%). titers of 0,5 IU There was no obvious relationship between the presence of neutralizing antibodies and the sex or age of the deer. Four of this animals were still live one year after the capture. The causes of dead of seven deer were tibia-tarsal dislocation, cervical vertebral dislocation, mites infestation and purulent pneumoniae. All the deaths were not related to rabies symptoms or suspect. This region presents a recent rabies historical in cattle and rabies positivity in insectivorous (Myotis nigricans) and vampire bats (Desmodus rotundus) Bats were observed eating and flying near the deer location, but no bats bites were observed in the animals.
The presence of rabies neutralizing antibodies was described in racoons (Carey & McLean,1983) correlated to epizooties of rabies. The authors relate that approximately 80% of naturally infected racoons did not succumb to infection and did develop neutralizing antibodies. Rosette & Gunson (1984) describes the neutralizing antibodies to rabies in skunks possible transmitted by bats .
The presence of rabies virus neutralizing antibodies in infected and clinically ill animals is observed only in the last period of the disease ( Campbell & Charlton, 1988). Clinical symptoms were not observed in the deers and four of this were still alive for one year, so we can suppose a low virus titre infection in the deers This region presents a recent rabies historical in cattle and rabies positivity in insectivorous (Myotis nigricans) bats. It´s important to consider that the wild deers can move as far as 50 km during the rain period and migration also occurs in bats . The habitat alteration by agriculture practice and hydro-electric power station construction, can facilitate the migration of animals (Sá,1992) and approximate cattle and bats . Although the wild deers prefer open areas they also can penetrate in the wood and remain in closed areas. Additionally, the immune response in animals feeding on infected material have been demonstrated experimentally( Bell & Moore,1971). The presence of bats feeding near the deers location was observed by several persons. Bat rabies and carnivore-rabies associations have been described by Constantine (1967) in vertebrates feeding on Brazilian free-tailed bats. Lord et al ( 1975) surveyed vampire bats and carnivores after an outbreak of rabies in cattle in Argentina. They have observed antibody positivity in cattle, in vampire bats, foxes and skunks and they speculated that the antibodies in the carnivores was a result of eating dead or dying rabid vampire bats.
The results suggests a low viral titer infection and subsequent production of rabies virus neutralizing antibodies by the cervideos, justified by the endemicity of rabies in the region with possibility of natural dissemination by bats.
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