Re-emergence of rabies virus maintained by canid populations in Paraguay.

Paraguay has registered no human cases of rabies since 2004, and the last case in dogs, reported in 2009, was due to a variant maintained in the common vampire bat "Desmodus rotundus". In 2014, a dog was diagnosed as positive for rabies with aggression towards a boy and all required measures of control were successfully adopted. Epidemiological investigation revealed that the dog was not vaccinated and had been attacked by a crab-eating fox, "zorro" (Cerdocyon thous). The sample was diagnosed by the Official Veterinary Service of the Country and sent to the Center on Rabies Research from the University of São Paulo, Brazil, for antigenic and genetic characterization. A second sample from a dog positive for rabies in the same region in 2015 and 11 samples from a rabies outbreak from Asuncion in 1996 were also characterized. The antigenic profile of the samples, AgV2, was compatible with one of the variants maintained by dogs in Latin America. In genetic characterization, the samples segregated in the canine (domestic and wild species)-related group in an independent subgroup that also included samples from Argentina. These results and the epidemiology of the case indicate that even with the control of rabies in domestic animals, the virus can still circulate in wildlife and may be transmitted to domestic animals and humans, demonstrating the importance of continuous and improved surveillance and control of rabies, including in wild species, to prevent outbreaks in controlled areas.

Vaccine immune response and interference of colostral antibodies in calves vaccinated against rabies at 2, 4 and 6 months of age born from antirabies revaccinated females.

Considering the high prevalence of rabies in cattle, we aimed to evaluate the interference of colostral antibodies transferred to calves after birth and the benefit of administering an antirabies vaccination in two-month-old calves compared to vaccinating at 4 and 6 months of age. Calves born from females revaccinated against rabies during the third trimester of pregnancy were studied. Forty-eight hours after parturition, blood samples from dams and offspring were collected, and antirabies neutralizing antibody titers were analyzed using the Rapid Focus Fluorescent Inhibition Test. We found that all calves had similar titers of antibodies transferred through the colostrum. Furthermore, none of the calves presented a satisfactory serological response after the first vaccination, but all had an appropriate response after revaccination. This study demonstrates that antirabies vaccination should be recommended for calves at two months of age in endemic and epizootic situations.

Importance of antirabies revaccination for an adequate antirabies protection in bovine newborns.

The transfer of antirabies immunoglobulins in cows that were prime vaccinated and cows that were revaccinated against rabies correlated to the serum titers in their offspring was evaluated. The results demonstrated that revaccination against rabies during pregnancy induces neutralizing antibody titers at a protective level that are transferred directly to calves through colostrum and reinforce the importance of revaccination for improved colostral antibody transfer and offspring protection against rabies.

Vaccinating the vampire bat Desmodus rotundus against rabies.

The objective of this study was to extend the previous work of indirect oral rabies immunization of vampire bats (Desmodus rotundus) maintained in captivity, which demonstrated the immunogenicity of the V-RG vaccine (Vaccinia-Rabies Glycoprotein) and indicated that although the results had been encouraging, a new method for concentrating the vaccine should be tested in order to avoid vaccine loss and increase the survival proportion of bats after rabies challenge. In this study, three groups of seven bats each were tested with vaccine concentrated by ultrafiltration through a cellulose membrane. The vaccine was homogenized in Vaseline paste and applied to the back of one vector bat, which was then reintroduced into its group. A dose of 10(5.0) MICLD(50) rabies virus was used by intramuscular route to challenge the bats postvaccination. The survival proportion in the three groups after the challenge was 71.4%, 71.4% and 100%.

Experimental rabies infection in haematophagous bats Desmodus rotundus.

In order to determine the susceptibility and serum neutralizing antibody response of Desmodus rotundus to rabies virus, bats were inoculated with a virus isolated from a naturally infected haematophagous bat. Bats were divided into four groups of 10 animals each. Dilutions of rabies virus containing 100, 1000, 10,000 and 100,000 MICLD50 (lethal dose 50% for mice inoculated by the intracerebral route) were administrated in the pectoral muscle. The presence of rabies virus was detected in brain and salivary glands by fluorescent antibody, mouse inoculation and RT-PCR. The observed mortality for each virus dose was 0, 20, 20 and 60% respectively. Serum neutralizing antibodies were tested for by the rapid fluorescent focus inhibition test, and antibody titres greater than 0.5 IU/ml were found in 53% of bats 30 days after virus inoculation. Resistance to infection was seen in bats that developed low or no detectable antibody response as well as in bats with high titres. Among the 10 bats that died of rabies, eight showed signs of paralytic rabies and two bats showed no clinical signs.

Neutralizing antirabies antibodies in urban terrestrial wildlife in Brazil.

The prevalence of rabies neutralizing antibodies (NA) in sera of wild animals from São Paulo City (Brazil) was investigated using the Rapid Fluorescent Focus Inhibition Test between 1994 and 1997. Sera from 547 specimens were examined. Marsupials represented 45% of the sample and primates 37%; carnivores, rodents, deer and edentates represented 6, 6, 3 and 2%, respectively. The overall prevalence of NA was 14%. The prevalence of NA was 18% in primates; whereas in marsupials, carnivores, edentates and rodents it was 13, 9, 8 and 6%, respectively. The stratification according to sex, age, and site of capture of the marsupials and primates showed a small predominance in males versus females and a large predominance of adults versus juveniles. The same relationship was seen in specimens captured near human habitations versus specimens captured in their own habitat. It is evident that there is circulation of rabies virus in wild animals, which are not recommended as pets since they represent a potential risk of exposure to rabies virus for both humans and domestic animals.

[Isolation of rabies virus from the insectivorous bat Myotis nigricans]. / Isolamento do vírus rábico de morcego insetívoro Myotis nigricans.

The following is a case study of the natural infection by the rabies virus of an insectiverous bat belonging to the species Myotis nigricans in the municipality of Ribeirão Pires, Greater S. Paulo. Diagnosis was made by means of immunofluorescence and intracerebral innoculation of mice with nervous and intrascapular muscular tissues.

[Laboratory diagnosis of rabies in chiroptera carried out in a metropolitan area of southeastern region Brazil]. / Diagnóstico laboratorial de raiva em quirópteros realizado em área metropolitana na região sudeste do Brasil.

Between January, 1988 and December, 1992 the S. Paulo Animal Disease Control Center subjected 289 bats to rabies examinations, utilizing the direct immunofluorescence and biological techniques. Two insectiverous bats belonging to the species Nyctinomops macrotis, representing 0.69% of the total sample, tested positive. Both animals had been captured alive in residential neighborhoods of the city, one in 1988 in the living room of a 7th floor apartment and the other in 1990 on top of a wall surrounding a private house. In the biological tests, the disease showed incubation periods of 13 and 11 days respectively. Although the existence of infected insectiverous bats in urban areas is cause for concern, indiscriminate predatory action against such species can in no way be justified-particularly bearing in mind their importance in preserving the ecological balance of the insect population so prevalent in cities.