Retrospective Evaluation of the Efficacy of the Measles Vaccine in Captive Western Lowland Gorillas (Gorilla gorilla gorilla)
Abstract
Due to their close phylogenetic relationship to humans, gorillas (Gorilla gorilla gorilla) are susceptible to a number of human pathogens, including measles virus. Clinical measles has not been documented in captive gorillas. However, the virus was implicated in a 1988 respiratory outbreak in wild mountain gorillas (Gorilla gorilla beringei) with some fatalities.1 This event has motivated the American Zoo and Aquarium Association and the American Association of Zoo Veterinarians to recommend the vaccination of all captive apes for measles.2-4
The most recent statement from the Gorilla Species Survival Plan recommends vaccination for measles at 15 months of age and again at 10–12 years of age.4 These recommendations are based on information extrapolated from human data and the knowledge that maternal antibodies can persist until 15 months of age in great apes.4 The current Lincoln Park Zoo measles vaccination protocol calls for vaccination (Attenuvax, Measles Virus Vaccine Live, Merck and Co., Inc., Whitehouse Station, NJ, USA; 0.5 ml IM) at 12 and 15 months of age, then again at 10 years of age. Unexposed, unvaccinated adults receive two doses of vaccine, separated by 2–4 weeks.
A review of the medical history from Western lowland gorillas at Lincoln Park Zoo revealed 28 vaccinated and 25 unvaccinated individuals in the collection. A retrospective analysis of available banked serum (1.0 ml) samples using a rapid dot-immunobinding assay (DIA), it was demonstrated that use of the vaccine led to the production of antibodies against the measles virus (OR 9.9; CI 1.75–60.52; P 0.003) (Tables 1 and 2). A sample was considered positive for antibodies if the DIA was greater than 1:10 (Cooke, A., Simian Diagnostic Laboratory, San Antonio, TX, USA, personal communication). No significant relationship was found between groups that received different numbers of vaccinations (one, two, or three) and the probability of seroconversion. The data suggested that antibodies can persist over a period of at least 11 years. This information may be useful in determining vaccination protocols for captive gorillas and in implementing preventive care in wild gorilla populations.
Table 1. Measles antibody titer results of vaccinated
gorillas at Lincoln Park Zoo as measured by rapid
dot-immunobinding assay (DIA) at a 1:10 dilution
|
Time periods
|
+
|
%
|
−
|
%
|
Total
|
|
Pre-vaccination
|
3a
|
33
|
6
|
66
|
9
|
|
<2 y post-vaccination
|
14
|
70
|
6
|
30
|
20
|
|
2–5 y post-vaccination
|
18
|
86
|
3
|
14
|
21
|
|
>5 y post-vaccination
|
9
|
100
|
0
|
0
|
9
|
aOne of these gorillas tested negative 6 months prior to this positive pre-vaccination titer; here, this gorilla is included only in the positive category.
Note: Data do not exist for each gorilla in each time period.
Table 2. Measles antibody titer results of nonvaccinated
gorillas at Lincoln Park Zoo as measured by rapid
dot-immunobinding assay (DIA) at a 1:10 dilution
|
Group
|
+
|
%
|
−
|
%
|
Total
|
|
Nonvaccinated
|
4
|
31
|
9
|
69
|
13
|
Literature Cited
1. Hastings, B. E., D. Kenny, L. J. Lowenstine, and J. W. Foster. 1991. Mountain gorillas and measles: ontogeny of a wildlife vaccination program. Proc. Am. Assoc. Zoo. Vet., Calgary, Canada, Pp. 198–205.
2. Junge, R. 1991. American Association of Zoo Veterinarians Infectious Disease Reviews: Preventive Medicine Recommendations. P. 19.
3. Loomis, M. R. 1990. Update of vaccination recommendations for nonhuman primates. Proc. Am. Assoc. Zoo. Vet., South Padre Island, Texas, Pp. 257–260.
4. Ogden, J., and D. Wharton (ed.). 1997. Management of gorillas in captivity: husbandry manual of the gorilla Species Survival Plan. Gorilla Species Survival Plan and the Atlanta/Fulton County Zoo, Inc., Atlanta, Georgia, Pp. 189–190.