Despite the existence of effective rabies vaccines for dogs, dog-transmitted human rabies persists and has reemerged in Africa. Two consecutive dog vaccination campaigns took place in Chad in 2012 and 2013 (coverage of 71% in both years) in the capital city of N'Djaména, as previously published. We developed a deterministic model of dog-human rabies transmission fitted to weekly incidence data of rabid dogs and exposed human cases in N'Djaména. Our analysis showed that the effective reproductive number, that is, the number of new dogs infected by a rabid dog, fell to below one through November 2014. The modeled incidence of human rabies exposure fell to less than one person per million people per year. A phylodynamic estimation of the effective reproductive number from 29 canine rabies virus genetic sequences of the viral N-protein confirmed the results of the deterministic transmission model, implying that rabies transmission between dogs was interrupted for 9 months. However, new dog rabies cases appeared earlier than the transmission and phylodynamic models predicted. This may have been due to the continuous movement of rabies-exposed dogs into N'Djaména from outside the city. Our results show that canine rabies transmission to humans can be interrupted in an African city with currently available dog rabies vaccines, provided that the vaccination area includes larger adjacent regions, and local communities are informed and engaged.

Rabies claims approximately 59,000 human lives annually and is a potential risk to 3.3 billion people in over 100 countries worldwide. Despite being fatal in almost 100% of cases, human rabies can be prevented by vaccinating dogs, the most common vector, and the timely administration of post-exposure prophylaxis (PEP) to exposed victims. For the control and prevention of human rabies in N’Djamena, the capital city of Chad, a free mass vaccination campaign for dogs was organized in 2012 and 2013. The campaigns were monitored by parallel studies on the incidence of canine rabies based on diagnostic testing of suspect animals and the incidence of human bite exposure recorded at selected health facilities. Based on the cost description of the campaign and the need for PEP registered in health centers, three cost scenarios were compared: cumulative cost-efficiency of (1) PEP alone, (2) dog mass vaccination and PEP, (3) dog mass vaccination, PEP, and maximal communication between human health and veterinary workers (One Health communication). Assuming ideal One Health communication, the cumulative prospective cost of dog vaccination and PEP break even with the cumulative prospective cost of PEP alone in the 10th year from the start of the calculation (2012). The cost efficiency expressed in cost per human exposure averted is much higher with canine vaccination and One Health communication than with PEP alone. As shown in other studies, our cost-effectiveness analysis highlights that canine vaccination is financially the best option for animal rabies control and rabies prevention in humans. This study also provides evidence of the beneficial effect of One Health communication. Only with close communication between the human and animal health sectors will the decrease in animal rabies incidence be translated into a decline for PEP. An efficiently applied One Health concept would largely reduce the cost of PEP in resource poor countries and should be implemented for zoonosis control in general.

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Objective: The objective of this study was to determine the prevalence, geographical distribution, and main risk factors for peste des petits ruminants (PPR) in the Republic of Chad. Materials and methods: A total of 3,546 sera collected from unvaccinated small ruminants including 1,699 goats and 1,847 sheep in 19 of the 23 regions in Chad were randomly sampled. The competitive enzyme-linked immunosorbent assay technics were used for serological analysis. Results: The overall seroprevalence at the individual level was 52.9%±1.6% (48.9% for goats and 56.2% for sheep). Seroprevalence observed in the Chari Baguirmi, Ouaddaï, and N’Djamena regions was significantly higher than those in the other regions. Transhumant herds are the most exposed than the sedentary ones. Older animals were more affected than the young ones. Kababich sheep are the most affected than other breeds. Conclusion: This study has shown that the PPR virus is circulating in the Republic of Chad. In view of the results obtained, the disease is enzootic in the country. Epidemiological information obtained including seroprevalence rate, risk factors (sex, breed, age, and mode of rearing), and geographical distribution will help to define an appropriate strategy for PPR control in the Republic of Chad.

RESUMEObjectif : Chaque année, la maladie de Newcastle (MN) apparaît spontanément dans les ménages ruraux à partir d'octobre à mai. Ce qui lui donne un caractère saisonnier. La connaissance des causes et des facteurs saisonniers de la manifestation de la maladie de Newcastle est un atout pour sa prévention. Méthodologie et résultats : Les rapports annuels et les études menées entre 1990 et 2006 ont constitué la base de documentation. En plus, en 2007 une enquête a été organisée dans neuf (9) villes et leur périphérie. Le choix des ménages a été fait au hasard et selon la disponibilité des producteurs. Des fiches d'enquête élaborées ont porté sur des informations relatives au climat ; à la mortalité des poulets, la période d'apparition de la MN, l'âge de la volaille affectée, la pratique d'élevage. Les données collectées ont été analysées à l'aide de l'outil informatique « Excel ». La moyenne mensuelle de température a varié entre 24 et 34°C ; la manifestation de la MN a été saisonnière avec trois périodes dans l'année : deux périodes de flambées allant de novembre à février et de mars à juin et une période d'accalmie allant de juillet à octobre. Conclusion et application : La saison, les pratiques d'élevage, la densité de volailles et l'activité humaine sont des facteurs favorisant l'apparition de la MN au Tchad. La saisonnalité de la MN est étroitement liée à la forte densité de volailles (reconstitution des poulets) et l'activité humaine (travaux champêtres). La connaissance des facteurs favorisant l'apparition de la MN est un outil important de prévention et de lutte contre cette maladie. Mots clés : Maladie de Newcastle, volaille, mortalité, saisonnalité, apparition Tchad. Factors promoting the onset of Newcastle disease in Chad ABSTRACTObjective: Each year, Newcastle disease (ND) occurs spontaneously in rural households from October to May. This gives it a seasonal nature. Knowledge of the causes and factors of seasonality of the occurrence of Newcastle disease is an asset for its prevention. Methodology and Results: Annual reports and studies undertaken between 1990 and 2006 have been a basic of documentation. In addition, in 2007 a survey has been conducted in nine (9) cities and their peripheries. The choice of households has been randomly selected and subject to availability of producers. Elaborated survey forms focused on information related to climate, mortality of chickens, period of onset of ND, age of affected birds and livestock practice. Collected data has been analyzed using the software tool "Excel." The average of monthly temperature varied between 24 and 34 ° C, The occurrence of ND has been seasonal with three periods in the year: two periods of outbreaks (November-February) and (March -June) and a period of lull (JulyOctober). Conclusion and application: The season, livestock density and human behavior are factors favoring the occurrence of ND in Chad. The seasonality of ND is closely related to the high density of chickens (restocking of Journal of Applied Biosciences 70:5591-5598