Ivanete Kotait

Rabies laboratory diagnosis: peculiar features of samples from equine origin

Rabies laboratory diagnosis is performed by using microscopic examination for Negri bodies (MEN), fluorescent-antibody test (FAT) and mouse inoculation test (MIT). In the majority of cases, when specimens are properly collected and conserved and the laboratory worker has good experience, agreement among employed techniques is verified. Comparing the sensitivity of these three diagnosis techniques in 3,713 samples (hippocampus and brain stem) received during 1981-1994 period, being 3,010 from bovine (983 positives) and 703 from equine (111 positives) species, it was observed that in equine rabid samples, this agreement was not maintained. For the latter specie, only in few opportunities the Negri bodies could be observed. With respect to FAT, the test detected a lower porcentage of positive equine samples compared to bovine species. Statistical analysis demonstrated that the difference was significative. Mouse inoculation test proved to be more sensitive. However, a significant difference in mice incubation period was observed for samples from both species. The absence of inclusion bodies and the longer incubation period for equine samples suggest that rabies pathogenesis studies for equine species have to be intensified.

Fluorescent antibody test, quantitative polymerase chain reaction pattern and clinical aspects of rabies virus strains isolated from main reservoirs in Brazil

Rabies virus (RABV) isolated from different mammals seems to have unique characteristics that influence the outcome of infection. RABV circulates in nature and is maintained by reservoirs that are responsible for the persistence of the disease for almost 4000 years. Considering the different pattern of pathogenicity of RABV strains in naturally and experimentally infected animals, the aim of this study was to analyze the characteristics of RABV variants isolated from the main Brazilian reservoirs, being related to a dog (variant 2), Desmodus rotundus (variant 3), crab eating fox, marmoset, and Myotis spp. Viral replication in brain tissue of experimentally infected mouse was evaluated by two laboratory techniques and the results were compared to clinical evolution from five RABV variants. The presence of the RABV was investigated in brain samples by fluorescent antibody test (FAT) and real time polymerase chain reaction (qRT-PCR) for quantification of rabies virus nucleoprotein gene (N gene). Virus replication is not correlated with clinical signs and evolution. The pattern of FAT is associated with RABV replication levels. Virus isolates from crab eating fox and marmoset had a longer evolution period and higher survival rate suggesting that the evolution period may contribute to the outcome. RABV virus variants had independent characteristics that determine the clinical evolution and survival of the infected mice.

Eficácia de vacina inativada contra a doença de Aujeszky: infecção experimental de suínos

Uma vacina experimental contra a doenca de Aujeszky (DA), inativada e adsorvida em adjuvante oleoso, foi testada em relacao a inducao de imunidade, grau de protecao clinica e capacidade de reduzir a infeccao, apos desafio pela via intranasal. Grupos de 6 suinos, com 45 dias de idade, foram vacinados com uma ou duas doses de vacina, pelas vias intramuscular ou subcutânea, sendo mantido um grupo-testemunha, sem vacinacao. Todos os suinos vacinados apresentaram titulos de anticorpos neutralizantes, detectaveis atraves da prova de soroneutralizacao, sendo estatisticamente superiores nos animais que receberam duas doses de vacina. A vacinacao preveniu as manifestacoes clinicas da doenca, apos desafio, principalmente nos animais que receberam duas doses de vacina quando comparado com os que receberam 1 dose. Em todos os animais, vacinados e nao-vacinados, foi possivel a deteccao do virus da doenca de Aujeszky (VDA) nas amigdalas, atraves da tecnica de imunofluorescencia direta. A porcentagem de amigdalas positivas nos suinos vacinados com duas doses foi inferior quando comparada aquela de suinos nao-vacinados, no 2o e 7o dias pos-infeccao. Em suinos vacinados com duas doses de vacina, pela via subcutânea, a taxa de infeccao foi estatisticamente menor que naqueles vacinados com uma dose, pelas vias intramuscular ou subcutânea, e nao-vacinados.

Antigenic Typing of Lyssaviruses by Monoclonal Antibodies

The application of monoclonal antibodies (MAbs) to antigenic typing of rabies virus (RABV) and, subsequently, its differentiation from other members of the Lyssavirus genus, was one of the most important developments in the applied research related to epidemiological laboratory-based surveillance of the disease at the end of the 1970s. This chapter describes the primary methods used for antigenic characterization and their application, mainly in developing countries.