Surveillance of Canine Rabies in the Central African Republic: Impact on Human Health and Molecular Epidemiology

Abstract

Background: Although rabies represents an important public health threat, it is still a neglected disease in Asia and Africa where it causes tens of thousands of deaths annually despite available human and animal vaccines. In the Central African Republic (CAR), an endemic country for rabies, this disease remains poorly investigated.

Methods: To evaluate the extent of the threat that rabies poses in the CAR, we analyzed data for 2012 from the National Reference Laboratory for Rabies, where laboratory confirmation was performed by immunofluorescence and PCR for both animal and human suspected cases, and data from the only anti-rabies dispensary of the country and only place where post-exposure prophylaxis (PEP) is available. Both are located in Bangui, the capital of the CAR. For positive samples, a portion of the N gene was amplified and sequenced to determine the molecular epidemiology of circulating strains.

Results: In 2012, 966 exposed persons visited the anti-rabies dispensary and 632 received a post-exposure rabies vaccination. More than 90% of the exposed persons were from Bangui and its suburbs and almost 60% of them were under 15-years of age. No rabies-related human death was confirmed. Of the 82 samples from suspected rabid dogs tested, 69 were confirmed positive. Most of the rabid dogs were owned although unvaccinated. There was a strong spatiotemporal correlation within Bangui and within the country between reported human exposures and detection of rabid dogs (P<0.001). Phylogenetic analysis indicated that three variants belonging to Africa I and II lineages actively circulated in 2012.

Conclusions: These data indicate that canine rabies was endemic in the CAR in 2012 and had a detrimental impact on human health as shown by the hundreds of exposed persons who received PEP. Implementation of effective public health interventions including mass dog vaccination and improvement of the surveillance and the access to PEP are urgently needed in this country.

Fig 1. Weekly distribution of the 69 canine rabies cases and the 966 human exposures to suspicious rabid dogs in the CAR in 2012.

In dark blue, the weekly numbers of persons exposed to suspicious rabid dogs, and in red, the weekly numbers of rabid dogs.

Fig 2. Spatial-temporal distribution of the 69 reported rabid dog cases, the 966 human exposures to suspicious rabid dogs, and the 632 post-exposure prophylaxes in the CAR in 2012.

In A), the spatial distribution of reported rabid dogs, in B), the spatial distribution of human exposures to suspicious rabid dogs, and in C), the numbers of reported rabid dogs, persons exposed to suspicious rabid dogs and post-exposure prophylaxes by month in the 16 administrative prefectures of the CAR (BAM: Bamingui Bangoran, BKO: Basse Kotto, HKO: Haute Kotto, HMB: Haut Mbomou, KEM: Kémo, LOB: Lobaye, MAM: Mambéré Kadéï, MBO: Mbomou, NGB: Nana Grébizi, NMA: Nana Mambéré, OMB: Ombella M'Poko, OUA: Ouaka, OUH: Ouham, OUP: Ouham Pendé, SAN: Sangha Mbaéré and VAK: Vakaga). In D), the spatial distribution of reported rabid dogs, in E), the spatial distribution of human exposures to suspicious rabid dogs, and in F), the numbers of reported rabid dogs, persons exposed to suspicious rabid dogs and prophylaxes by month in the eight urban districts of Bangui (1 to 8) and in Bégoua and Bimbo. In red, the rabid dogs, in dark blue, the persons exposed to suspicious rabid dogs, and in light blue, the persons who received a prophylaxis.

Fig 3. Distribution of the number of persons exposed to suspicious rabid dogs according to the presence of rabid dogs reported the same week in the same area.

In A), if no rabid dog was identified in the same area the same week, and in B), if at least one rabid dog was reported in the same area the same week.

Fig 4. Molecular phylogenetic analysis of representative RABV isolated in the CAR during the year 2012 and their geographical distribution.

The neighbor-joining method was used for reconstructing the tree of the N gene sequences of reference RABV strains from Africa I, II and III clades and new sequences from the CAR identified in this study. The percentages of replicate trees in which the isolates clustered together in the bootstrap test (1000 replicates) are shown next to the branches.