[Rabies]

Spatiotemporal dynamics of rabies virus detected in rabid dogs in Cameroon, 2010-2021

Rabies is a viral zoonosis that causes an estimated 60,000 human deaths each year, mainly in Africa and Asia. The etiological agent of rabies, the Rabies Lyssavirus or Rabies Virus (RABV) has been characterized in dog populations in Cameroon, in previous studies. However, the dynamics of RABV maintenance and propagation in dogs are still to be documented in Cameroon. This study thus, aimed at investigating the spatial and temporal dynamics of RABV variants in Cameroon. Long genomic sequences of about 4893 nucleotides, encompassing the N, P, M and G genes as well as part of the G-L intergenic region (Ψ), were determined from 56 RABV strains recovered from dog populations in Cameroon from 2010 to 2021. Temporal and spatial dynamics of RABV circulation in Cameroon were investigated by Bayesian analyses with the BEAST 1.10.4 package from extended RABV genomic sequences data combined with their collection dates and the geographical coordinates of their sampling areas. This revealed a genetic evolution rate of 3.14 × 10-4 substitutions/site/year among Africa-1a and Africa-2 clades of RABV from Cameroon. The most recent common ancestor (MRCA) of the studied strains of the Africa-1a lineage was estimated to have emerged between 1880 and 1906 (95 % HPD; mean 1894), while that of the strains of the Africa-2 clade had a slightly later estimated origin between 1907 and 1928 (95 % HPD, mean 1918). Overall, phylogeographic analyses suggested RABV spread in Cameroon between sub-national regions. Our data provides substantial support to previous findings from similar epidemiological settings, indicating human mediated movements of infected dogs between distant cities may be a key factor in the maintenance of the enzootic cycle of rabies among dogs in Cameroon.

Rabies surveillance and prevention in Guinea: Epidemiological data and postexposure prophylaxis challenges

Background and Aim

Canine rabies is an endemic form of zoonosis and represents a major public health threat in Guinea, similar to other African countries. However, few investigations on the epidemiology of rabies in animals and humans have been conducted, and evidence-based data required to inform health policies remain inadequate. This study was conducted to update our knowledge of human dog-mediated rabies epidemiology and post-exposure prophylaxis (PEP) accessibility-related factors in Guinea.

Materials and Methods

This retrospective study, conducted from January 2018 to December 2020, collected data on animal bite cases, veterinary observations, rabies diagnoses through fluorescent antibody test, and PEP delivery from three veterinary and medical entities. Statistical analysis utilized Chi-square test and Fisher's exact test to evaluate relationships between variables.

Results

An average of 775 bites was recorded annually, and dogs were responsible for 98% of bites. However, only 64% of the biting dogs were under veterinary observation as required for integrated bite case management. Regarding the geographical distribution of bite cases, the entire country was affected, with the highest number of bites recorded in the prefectures of Nzérékoré and the special zone of Conakry. In addition, the laboratory diagnosis of brain samples from biting dogs indicated that 72% of the samples were rabies-positive. However, regarding prevention, only 58% of the bitten individuals received full PEP.

Conclusion

Improving disease surveillance and PEP provision for dog-transmitted rabies is crucial to preventing human cases and deaths. Increasing community awareness is essential for enhancing dog vaccination and PEP utilization. A national action plan integrating stakeholders for controlling canine rabies should be developed for effective One Health collaboration.

Filter Papers to Collect Blood Samples from Dogs: An Easier Way to Monitor the Mass Vaccination Campaigns against Rabies?

Rabies is a deadly viral disease present mainly in low-income countries of Africa and Asia. Dogs are the main reservoir and the source of human deaths. Mass vaccination campaigns of dogs are pivotal to achieve rabies elimination. The monitoring of the immune response of the dog population is necessary to evaluate the effectiveness of these campaigns, taking into account field conditions. This study explores the feasibility and the performance of a new tool using filter papers (FPs) to collect blood samples associated with an Enzyme-Linked ImmunoSorbent Assay (ELISA) titration of rabies antibodies in dogs. A total of 216 eluates from FP samples were collected from 111 dogs kept in experimental facilities in France and 29 dogs from the field in Tunisia. Sera were also analyzed using both the Fluorescence Antibody Virus Neutralization test (FAVNt) and ELISA. A high specificity (98.0%) was obtained by testing FP blood eluates from 51 unvaccinated dogs, with the results compared with those of FAVNt and ELISA on serum samples. The coefficients of concordance between FP eluates and tested sera were 88.9% for FAVNt and 88.0% for ELISA. Blood filter papers coupled with the titration of rabies antibodies by ELISA provide a reliable, simple, and effective solution to overcome the issues of the logistics and transport of samples, especially in low-income countries.

Modelling the factors affecting the probability for local rabies elimination by strategic control

Dog rabies has been recognized from ancient times and remains widespread across the developing world with an estimated 59,000 people dying annually from the disease. In 2011 a tri-partite alliance consisting of the OIE, the WHO and the FAO committed to globally eliminating dog-mediated human rabies by 2030. Regardless of global support, the responsibility remains with local program managers to implement successful elimination programs. It is well known that vaccination programs have a high probability of successful elimination if they achieve a population-coverage of 70%. It is often quoted that reducing population turnover (typically through sterilizations) raises the probability for local elimination by maintaining herd immunity for longer. Besides this, other factors that affect rabies elimination are rarely mentioned. This paper investigates the probability for local elimination as it relates to immunity, fecundity, dog population size, infectivity (bite rates), in-migration of immune-naïve dogs, and the initial incidence. To achieve this, an individual-based, stochastic, transmission model was manipulated to create a dataset covering combinations of factors that may affect elimination. The results thereof were analysed using a logistic regression model with elimination as the dependent variable. Our results suggest that smaller dog populations, lower infectivity and lower incidence (such as when epidemics start with single introductions) strongly increased the probability for elimination at wide ranges of vaccination levels. Lower fecundity and lower in-migration had weak effects. We discuss the importance of these findings in terms of their impact and their practical application in the design of dog-mediated rabies control programs.

Most guidelines for rabies control call for at least 70% vaccination coverage of dogs. This level of immunity has a very high probability for the local elimination of rabies, but it is often not an achievable ideal due to resource constraints. Campaign managers can be strategic on how they allocate their resources. Lower infectivity rates are present in areas with more restricted dog movements and have higher probabilities for elimination at lower vaccination rates. Smaller sub-populations have higher probabilities for elimination at the same vaccination coverage levels compared to larger sub-populations. Vaccinating immune corridors can divide meta-populations into smaller sub-populations that are likely to result in elimination either due to their small size or due to the local low infectivity. Areas already free of rabies require lower vaccination levels to maintain freedom compared to endemic areas. Where donors do not specifically require sterilization campaigns, funds meant for rabies control should not be diverted to sterilizations.

Risk factors for rabies in Côte d'Ivoire

Rabies affects more than 150 countries worldwide. Côte d'Ivoire is one of the rabies-endemic countries that has recorded deaths every year since 2006. The evolution of these deaths is almost constant with an average of 18 annual deaths (annual incidence = 0.06-0.08 per 100,000). Children predominate among these victims. However, prevention measures exist in anti-rabies centers distributed throughout the country. The objective of this study was to determine the factors related to rabies risk in Côte d'Ivoire through Gavi rabies project entitled 'Impact of rabies and immunization in Central and West Africa'. The implementation was conducted from 2016 to 2018 in two departments of Côte d'Ivoire (Bouake and San Pedro). The study population was dog-bite victims vaccinated in anti-rabies centers of project sites from January to December 2016. Two non-free rabies immunization protocols are used in the country (Essen and Zagreb). Information was collected from bites victims for an adequate follow-up. It was to apprciate the risk of developing rabies through access to care, the immunization status of biting animal, the category of exposure and the result of rabies post exposure prophylaxis (compliance). Local program implementers responsible for these bite-management activities and veterinary staff had receved training and the necessary material. The public health education and information dissemination activities were carried out in support of promoting a wide spread of rabies prevention messages. Household surveys were conducted by sociology students in 4002 households each in urban and in rural areas. This activity helped to find people exposed by dogs and who did not receive any Post Exposure Prophylaxis (PEP). The study registered 1,263 bite victims in pilot anti-rabies centers in 2016, 51% of them were children. People living in urban areas were strongly represented (87%) because of anti-rabies centers proximity. Dog was the most animal associated to exposure (94%). Seventy-two percent (72%) of them had owners, but only 14% were vaccinated against rabies. More than half of dog bite victims had category III of exposure (58%). PEP compliance record was very low (37%), which means that 63% of bite victims have not completed the protocol. This study conducted in Bouaké and San Pedro showed somes factors responsible for rabies deaths evolution in Côte d'Ivoire. Main issues identified are the geographical accessibility of anti-rabies centers, frequent bites caused by unvaccinated dogs, often category III of exposure and many non-completions of rabies PEP in ignorance context. The establishment of national comprehensive and integrated rabies control program is needed in Côte d'Ivoire. It must take into account all these factors by focusing on public awareness, dog vaccination and adoption of modern intradermal vaccination regimens to better manage rabies situation in Côte d'Ivoire.

Molecular study of rabies virus in slaughtered dogs in Billiri and Kaltungo local government areas of Gombe state, Nigeria

Rabies is one of the most dreadful diseases and a major viral zoonosis which has been shown to cause an almost 100% fatality rate in infected victims. It is characterized by acute progressive encephalitis in mammals. This study determined the genotypic characteristics of rabies virus in dogs slaughtered for human consumption based on sequence of a fragment of nucleoprotein gene. Brain tissues were collected from 50 dogs slaughtered in Billiri and Kaltungo Local Government Areas of Gombe State, Nigeria. Direct fluorescent antibody test (DFAT) was used to screen for the presence of rabies virus antigen. Viral RNA isolated from DFAT positive brain tissues were subjected to the reverse transcription polymerase chain reaction (RT-PCR) followed by sequencing of the amplicons. Maximum Likelihood (ML) was used to construct a phylogenetic tree for sequences obtained with 1000 bootstrap replicates. The DFAT detected rabies antigen in 3 (6%) of the 50 dog brain tissues, from which 1 (2%) was positive by RT-PCR. ML phylogeny approach of the nucleotide sequences inferred members as originating lyssavirus genus and dog species. Essentially, MK234794 in this study displayed 99.3% sequence similarity with other related rabies viruses in the Africa 2 cluster (Nigeria, Cameroon, Chad and Niger). Interestingly, MK234794 showed no cluster relation with the Africa 1a, 1b, 3 and Africa 4 clades, respectively. This indicates there is in-country and trans-boundary circulation of the rabies viruses with no co-circulation between the Africa lineages, especially as dogs are continuously being traded due to consumption of dog meat in West Africa. This finding has given additional insight into the molecular epidemiology of rabies virus in Nigeria, therefore providing more baseline information for future design of rabies control programs in the country.

Dog demographics and husbandry practices related with rabies in Cameroon

Dog demographics are considered as one of the main factors in the control of rabies. Having reliable data on dog population and husbandry practices on how they are managed is a key point in the elaboration of any control program to fight against human deaths due to rabies which are mainly due to dogs. However, the lack of data regarding dog population is one of the main hindrances to elaborate effective fighting projects in developing countries, particularly in Africa. In order to contribute for reliable data on dog demographics and husbandry practices related to rabies, this study was carried out in the cities of Ngaoundéré, Garoua and Yaoundé, respectively located in Adamaoua, North and Centre regions of Cameroon from October 2013 to April 2014. A survey was conducted within 2500 households selected randomly to which 45 questions were addressed, while the vaccine status of dogs was checked in the houses by verifying the vaccination booklet and in public and private veterinary clinics. Various aspects of dogs such as dog population, husbandry practices, ownership and age distribution were assessed. Out of these households, 45% of them (1118) had exploitable data. From these, 46% of them owned at least 1 dog for a total of 707 dogs, with a dog per household ratio of 6.3:10 for a dog per human ratio of 1.16:10. The age distribution of these dogs showed that the mean age of male and female was around 2 years with a male per female ratio of 29:10. The estimation of roaming dogs gave a ratio of 2.3:10 per human. Concerning the reasons for having a dog, the main motivation was guarding (76%) and company (17%). Husbandry practices applied to these dogs were a complete restrained (52%), semi-restrained (29%) and a complete roaming (18%). In relation to rabies, only 34% of dog owners were able to prove the effective vaccination of their dogs and no reason was given to explain the non-vaccination by the majority (78%) of the owners. So this study provides for the first time a baseline on dog population for an objective fighting program but also shows that the husbandry practices applied by the owners can be a hindrance to a fighting program against rabies.

Molecular characterization and phylogenetic relatedness of dog-derived Rabies Viruses circulating in Cameroon between 2010 and 2016

Rabies is enzootic among dog populations in some parts of Cameroon and the risk of human rabies is thought to be steadily high in these regions. However, the molecular epidemiology of circulating Rabies Virus (RABV) has been hardly considered in Cameroon as well as in most neighboring central African countries. To address this fundamental gap, 76 nucleoprotein (N) gene sequences of dog-derived RABV were obtained from 100 brain specimens sampled in Cameroon from 2010 to 2016. Studied sequences were subjected to molecular and phylogenetic analyses with reference strains retrieved from databases. The 71 studied Africa-1 isolates displayed 93.5–100% nucleotide (nt) and 98.3–100% amino-acid (aa) identities to each other while, the 5 studied Africa-2 isolates shared 99.4–99.7% sequence similarities at nt and aa levels. Maximum Likelihood based phylogenies inferred from nucleotide sequences confirmed all studied RABV isolates as members of the dog-related species 1 of the Lyssavirus genus. Individual isolates could be unambiguously assigned as either the Africa-1 subclade of the Cosmopolitan clade or the Africa 2 clade. The Africa-1 subclade appeared to be more prevalent and diversified. Indeed, 70 studied isolates segregated into 3 distinct circulating variants within Africa-1a lineage while a unique isolate was strikingly related to the Africa-1b lineage known to be prevalent in the neighboring Central African Republic and eastern Africa. Interestingly, all five Africa-2 isolates fell into the group-E lineage even though they appeared to be loosely related to databases available reference RABV; including those previously documented in Cameroon. This study uncovered the co-circulation of several Africa-1 and Africa-2 lineages in the southern regions of Cameroon. Striking phylogenetic outcasts to the geographic differentiation of RABV variants indicated that importation from close regions or neighboring countries apparently contributes to the sustainment of the enzootic cycle of domestic rabies in Cameroon.

Rabies has been repeatedly reported among dog populations in Cameroon, especially in Yaounde, its capital city. However, the relative rates and genetic variability of Rabies Virus (RABV) variants circulating among dog populations in Cameroon are still to be documented. This study aimed to estimate the frequency and genetic diversity of RABV isolates originating from rabid dogs in the southern regions of Cameroon from 2010 to 2016. Overall, 76 of the 100 dog-derived RABV isolates sampled in Cameroon from 2010 to 2016 were successfully characterized. Our findings revealed that studied isolates belonged to the dog-related species 1 of the Lyssavirus genus, specifically 70 Africa-1a, 1 Africa-1b and 5 Africa-2 group-E lineages. The general phylogenetic pattern suggested an in-country geographic differentiation of the circulating RABV variants. This apparent geographic differentiation was contradicted by striking outcasts indicating importation from close or distant regions. Overall, this study uncovered the co-circulation of several Africa-1 and Africa-2 lineages in some southern regions of Cameroon, thus providing base-line molecular data that would be of interest for future stages of implementation of the rabies surveillance and control plan that is being setup in Cameroon.

Cost-effectiveness of rabies post-exposure prophylaxis in the context of very low rabies risk: A decision-tree model based on the experience of France

INTRODUCTION

Benefit-risk of different anti-rabies post-exposure prophylaxis (PEP) strategies after scratches or bites from dogs with unknown rabies status is unknown in very low rabies risk settings.

DESIGN AND SETTING

A cost-effectiveness analysis in metropolitan France using a decision-tree model and input data from 2001 to 2011.

POPULATION

A cohort of 2807 patients, based on the mean annual number of patients exposed to category CII (minor scratches) or CIII (transdermal bite) dog attacks in metropolitan France between 2001 and 2011.

INTERVENTIONS

Five PEP strategies: (A) no PEP for CII and CIII; (B) vaccine only for CIII; (C) vaccine for CII and CIII; (D) vaccine+ rabies immunoglobulin (RIG) only for CIII; and (E) vaccine for CII and vaccine+ RIG for CIII.

MAIN OUTCOMES MEASURES

The number of deaths related to rabies and to traffic accidents on the way to anti-rabies centers (ARC), effectiveness in terms of years of life gained by reducing rabies cases and avoiding traffic accidents, costs, and incremental cost-effectiveness ratios (ICER) associated with each strategy.

RESULTS

Strategy E led to the fewest rabies cases (3.6 × 10(-8)) and the highest costs (€ 1,606,000) but also to 1.7 × 10(-3) lethal traffic accidents. Strategy A was associated with the most rabies cases (4.8 × 10(-6)), but the risk of traffic accidents and costs were null; therefore, strategy A was the most effective and the least costly. The sensitivity analysis showed that, when the probability that a given dog is rabid a given day (PA) was > 1.4 × 10(-6), strategy D was more effective than strategy A; strategy B became cost-effective (i.e. ICER vs strategy A < 3 × French Gross Domestic Product per capita) when PA was > 1 .4 × 10(-4).

CONCLUSIONS

In the metropolitan France's very low rabies prevalence context, PEP with rabies vaccine, administered alone or with RIG, is associated with significant and unnecessary costs and unfavourable benefit-risk ratios regardless to exposure category.