Use of a Direct, Rapid Immunohistochemical Test for Diagnosis of Rabies Virus in Bats

Rabies, a zoonotic encephalitis due to transmission of a lyssavirus, such as rabies virus (RABV), has the highest case fatality of any infectious disease. A global program for the elimination of human rabies caused by dogs is proposed for realization by 2030. Sensitive, specific, and inexpensive diagnostic tests are necessary for enhanced surveillance to detect infection, inform public health and veterinary professionals during risk assessments of exposure, and support overall programmatic goals. Multiple laboratory techniques are used to confirm a suspect case of rabies. One method for the detection of lyssavirus antigens within the brain is the direct rapid immunohistochemical test (dRIT), using light microscopy, and suitable for use under field conditions. Besides dogs, other major RABV reservoirs reside among mammalian mesocarnivores and bats. To date, use of the dRIT has been applied primarily for the diagnosis of RABV in suspect mesocarnivores. The purpose of this study was to assess the usefulness of the dRIT to the diagnosis of rabies in bats, compared to the gold-standard, the direct fluorescent antibody test (DFAT). Brains of 264 suspect bats, consisting of 21 species from Arizona and Texas, were used in the evaluation of the dRIT. The overall sensitivity of the dRIT was 100% (0.969–1.0, 95% CI) and the specificity was 94.6% (0.896–0.976, 95% CI), comparable to the DFAT. This preliminary study demonstrated the utility of the dRIT in the confirmation of RABV infection in bats. Future studies should include additional geographic, lyssavirus, and mammalian species representations for broader application during enhanced rabies surveillance, with incorporation of any potential adjustments to standard protocols, as needed.

PREVALENCE OF TOXOPLASMOSIS AMONG SHEEP AND GOATS IN BAGHDAD AREA

The complement fixation test (CFT) and the direct fluorescent antibody test were used for detecting anti Toxoplasma gondii antibodies in sera obtained from 143 sheep and 44 goats. Complement fixing antibodies were detected in 38 (26.2%) for sheep sera and 24 (54.5%) of goat sera tested by CFT. On the other hand, 26(18.2%) of sheep sera were positive by the FAT. The combined use of CFT and FAT allows the differentiation between an acute or latent T.gondii infection.

Detection of rabies virus antigen in brain tissue of dogs slaughtered for human consumption in Taraba State, Nigeria

Rabies as an ancient zoonosis constitutes a threat to public health by causing over 59,000 annual human mortalities worldwide. The aim of this study was to detect rabies virus in brain tissue of dogs slaughtered for human consumption in Taraba State, Nigeria. A total of 150 dogs comprising 136 adults and 14 puppies consisting of 82 males and 68 females was sampled from slaughter points in five Local Government Areas. Brain samples were collected from each dog in labeled sterile sample bottles and screened for rabies virus antigen using direct fluorescent antibody test (DFAT). Results showed that 3 out of the 150 (2%) brain samples screened were positive for rabies virus; out of which 2 were from Unguwan Kasa (14.3%) and 1 was from Quarter Five (7.1%). This therefore suggests the presence of rabies virus in dogs slaughtered for human consumption in Taraba State, Nigeria and their role as reservoirs of the virus. Therefore, there is need for awareness education on safe handling of dog meat to minimize the risk for butchers/meat handlers. Keywords: Brain samples, dogs, Prevalence, Rabies, Taraba State

Clinical Presentation and Serologic Response during a Rabies Epizootic in Captive Common Vampire Bats (Desmodus rotundus)

We report mortality events in a group of 123 common vampire bats (Desmodus rotundus) captured in México and housed for a rabies vaccine efficacy study in Madison, Wisconsin. Bat mortalities occurred in México and Wisconsin, but rabies cases reported herein are only those that occurred after arrival in Madison (n = 15). Bats were confirmed positive for rabies virus (RABV) by the direct fluorescent antibody test. In accordance with previous reports, we observed long incubation periods (more than 100 days), variability in clinical signs prior to death, excretion of virus in saliva, and changes in rabies neutralizing antibody (rVNA) titers post-infection. We observed that the furious form of rabies (aggression, hyper-salivation, and hyper-excitability) manifested in three bats, which has not been reported in vampire bat studies since 1936. RABV was detected in saliva of 5/9 bats, 2–5 days prior to death, but was not detected in four of those bats that had been vaccinated shortly after exposure. Bats from different capture sites were involved in two separate outbreaks, and phylogenetic analysis revealed differences in the glycoprotein gene sequences of RABV isolated from each event, indicating that two different lineages were circulating separately during capture at each site.