Exposure of hooded capuchin monkeys (Cebus apella cay) to a rabid bat at a zoological park

Unexpected rabies variant identified in kinkajou (Potos flavus), Mato Grosso, Brazil

A second case of a novel rabies variant described once in a capuchin monkey from Mato Grosso, Brazil, was discovered in a rabid wild kinkajou from the same region, indicating a public health risk following exposure to either of the two animals.

Susceptibility and lack of evidence for a viremic state of rabies in the night owl monkey, Aotus nancymaae

BACKGROUND

Rabies causes an acute fatal encephalomyelitis in most mammals following infection with rhabdovirus of the genus Lyssavirus. Little is known about rabies virus infection in species of New World non-human Primates (NHP). To investigate the suitability of the owl monkey Aotus nancymaae asissue sections examined were unremarkable for inflammation or other histologic signs of rabies a viable animal model for rabies virus candidate vaccine testing, we used clinical presentation, serology, viral isolation, and PCR to evaluate the incubation period, immunity, and pathogenesis of infected animals. We tested the hypothesis that no viremic state exists for rabies virus.

METHODS

Eight monkeys divided into two equal groups were inoculated intramuscularly either in the neck or footpad with 105 pfu of rabies virus (Pasteur/V-13R) and observed for >130 days. Oral and blood samples were collected and analyzed.

RESULTS

Two monkeys inoculated in the neck displayed classic paralytic rabies. The mean incubation period was 11.5 days. The average maximum IgG response (antibody titer >0.200 O.D.) was achieved at day 10.0 and 62.3 in the clinical rabies and non-clinical rabies cases, respectively (p = 0.0429). No difference in IgM or IgG time to seroconversion or average maximum IgM level was observed between neck versus footpad inoculation groups. No viremia or viral shedding was detected by PCR or viral isolation during the observation period, including within the two symptomatic animals three days after disease onset. Tissue sections examined were unremarkable for inflammation or other histologic signs of rabies within the asymptomatic animal. Similarly none of the brain sections exhibited immunoreactivity for rabies virus antibody.

DISCUSSION

This study demonstrates there is no difference in time to immune response between inoculation sites and distance to the brain; however, immune response tends to be more rapid in cases of clinically apparent disease and prolonged in cases infected at sites further from the brain.

CONCLUSIONS

Our findings support the hypothesis that a viremic state for rabies does not exist in the New World Monkey, Aotus nancymaae, and it appears that this species may be refractory to infection. The species does provide a suitable model to assess post infection immune responses. Additional studies that address the limitations of sample size, length of observation, and lack of measurable infection should be conducted.

Exposure to rabies virus in a population of free-ranging capuchin monkeys (Cebus apella nigritus) in a fragmented, environmentally protected area in southeastern Brazil

The aim of this study is to assess the frequency of rabies antibodies in free-ranging capuchin monkeys (Cebus apella nigritus) in a fragmented, environmentally protected, rural area of southeastern Brazil. Thirty-six free-ranging monkeys were tested by the rapid fluorescent focus inhibition test for detection of antibodies against rabies virus. Four individuals (11.11 %) had neutralizing antibody titers ≥ 0.25 IU/mL, demonstrating rabies virus exposure.

Surveillance of rabies prevalence and bite protocols in captive mammals in American zoos

A national survey questionnaire was conducted in 32 zoos throughout 17 U.S. states between February and May 2008. The questionnaire consisted of six questions that evaluated rabies prevalence on zoo grounds; captive mammalian bites among zoo visitors and personnel; and the outcome of each incident. The survey was completed by zoo staff after review of their most recent bite incident reports. Rabies was documented, albeit minimally, on zoo grounds in both wild and collection animals. The information collected documented that mammalian bites occur commonly. An average of 9.1 bite incidents per zoo involving zoo visitors were reported in the last 5 yr, compared to an average of 7.5 bite incidents per zoo involving personnel within the last 5 yr. Zoo personnel had a larger variety of mammals inflicting bites of greater injury severity, with an average rating 3.83 out of 5. While victim profile and severity of the wound differed between visitor and personnel bites, the majority of bites were not reported to the local health department. Lack of reporting may be due to low rabies risk, fear of media involvement, and an unknown conclusion for the offending animal. Animals involved in reported attacks had an average quarantine of 47.5 days when the bite involved a zoo visitor versus an average quarantine of 18 days when the bite involved personnel. These results demonstrate the need for a standardized protocol following a bite incident, including cooperation with the local health department, as necessary.

Results of vaccination of Asian elephants (Elephas maximus) with monovalent inactivated rabies vaccine

OBJECTIVE

To evaluate the humoral immune response of Asian elephants to a primary IM vaccination with either 1 or 2 doses of a commercially available inactivated rabies virus vaccine and evaluate the anamnestic response to a 1-dose booster vaccination.

ANIMALS

16 captive Asian elephants.

PROCEDURES

Elephants with no known prior rabies vaccinations were assigned into 2 treatment groups of 8 elephants; 1 group received 1 dose of vaccine, and the other group received 2 doses of vaccine 9 days apart. All elephants received one or two 4-mL IM injections of a monovalent inactivated rabies virus vaccine. Blood was collected prior to vaccination (day 0) and on days 9, 35, 112, and 344. All elephants received 1 booster dose of vaccine on day 344, and a final blood sample was taken 40 days later (day 384). Serum was tested for rabies virus-neutralizing antibodies by use of the rapid fluorescent focus inhibition test.

RESULTS

All elephants were seronegative prior to vaccination. There were significant differences in the rabies geometric mean titers between the 2 elephant groups at days 35, 112, and 202. Both groups had a strong anamnestic response 40 days after the booster given at day 344.

CONCLUSIONS AND CLINICAL RELEVANCE

Results confirmed the ability of Asian elephants to develop a humoral immune response after vaccination with a commercially available monovalent inactivated rabies virus vaccine and the feasibility of instituting a rabies virus vaccination program for elephants that are in frequent contact with humans. A 2-dose series of rabies virus vaccine should provide an adequate antibody response in elephants, and annual boosters should maintain the antibody response in this species.