Study on seroprevalence and serotyping of foot and mouth disease in Chad.

Foot and mouth disease (FMD) is a highly contagious viral disease that affects all Artiodactyla. Seven immunologically distinct serotypes of FMD virus (FMDV) exist. In Chad, although FMD is included in the list of diseases monitored by the Chadian Animal Disease Surveillance Network (REPIMAT), the epidemiological situation remains unclear. A serological survey was conducted in the cattle population in eight of the nine administrative regions of the country (those regions with the highest cattle densities), to evaluate the prevalence and serotypes of circulating FMDV.A total of 796 sera from randomly selected cattle were analysed at the World Organisation for Animal Health/Food and Agriculture Organization of the United Nations FMD Reference Laboratory at the Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna(IZSLER), in Brescia (Italy). An enzyme-linked immunosorbent assay (ELISA), called 3ABC ELISA, was used to detect antibodies against non-structural proteins (NSPs), as well as a series of six competitive ELISAs to detect and serotype antibodies against the structural proteins of FMDV serotypes O, A, SAT 1, SAT 2, Asia 1 and C. Based on the detection of anti-NSP antibodies, the animal-level seroprevalence was 35.6%(95% confidence interval [CI]: 32.2-38.9) and the herd-level seroprevalence was 62.3% (95%CI: 53.0-71.5). FMD was present in all livestock administrative divisions surveyed, with a higher prevalence in southern regions, which are characterised by higher rainfall and humidity and more important transboundary animal movements. Cattle aged more than four years had a higher seroprevalence, which may be due to repeated exposure. Semi-sedentary farming and transhumance were also risk factors. Antibodies against serotypes A, O, SAT 1 and SAT 2 were detected.

La fièvre aphteuse est une maladie virale extrêmement contagieuse qui affecte l'ensemble des artiodactyles. Sept sérotypes du virus de la fièvre aphteuse ont été répertoriés, qui sont distincts au plan immunologique. Au Tchad, bien que la fièvre aphteuse figure sur la liste des maladies visées par le Réseau d'épidémiosurveillance des maladies animales du Tchad (REPIMAT), la situation épidémiologique demeure mal connue. Une enquête sérologique a été réalisée dans la population bovine de huit régions administratives sur les neuf que compte le pays (afin de couvrir les régions où la densité de la population bovine est la plus élevée), dans le but d'évaluer la prévalence du virus de la fièvre aphteuse et de caractériser les sérotypes présents. Au total, 796 sérums prélevés sur des bovins sélectionnés de manière aléatoire ont été analysés au Laboratoire de référence pour la fièvre aphteuse de l'Organisation mondiale de la santé animale/Organisation des Nations Unies pour l'alimentation et l'agriculture à l'Istituto Zooprofilattico Sperimentale dellaLombardia e dell'Emilia Romagna (IZSLER) de Brescia (Italie). Les anticorps dirigés contre les protéines non structurales ont été détectés au moyen d'une épreuve immuno-enzymatique 3ABC (ELISA 3ABC) tandis qu'une série de six ELISA de compétition a permis de détecter et de caractériser les anticorps spécifiques des protéines structurales des sérotypes O, A, SAT 1, SAT 2, Asia 1 et C du virus de la fièvre aphteuse. D'après les résultats de la détection d'anticorps dirigés contre les protéines non structurales, la prévalence sérologique à l'échelle individuelle était de35,6 % (avec un intervalle de confiance [IC] à 95 % de 32,2 à 38,9) tandis que la prévalence à l'échelle des troupeaux s'élevait à 62,3 % (IC à 95 % de 53,0 à 71,5).La fièvre aphteuse était présente dans chacune des divisions administratives étudiées, avec une prévalence plus élevée dans les régions méridionales, qui se caractérisent par des précipitations et une hygrométrie plus fortes et par l'importance des mouvements transfrontaliers d'animaux. La prévalence sérologique était plus élevée chez les bovins âgés de plus de quatre ans, ce qui s'explique probablement par un nombre répété d'expositions. Le rôle de l'élevage semi-sédentaire et de la transhumance en tant que facteurs de risque a été misen lumière. Les anticorps détectés étaient dirigés contre les sérotypes A, O, SAT 1et SAT 2.

La fiebre aftosa es una patología vírica muy contagiosa que afecta a todos los artiodáctilos. Existen siete serotipos inmunológicamente diferenciados del virus que la causa. En el Chad, aunque la fiebre aftosa figura en la lista de enfermedades sometidas a vigilancia por la Red Chadiana de Vigilancia Zoosanitaria (REPIMAT), la situación epidemiológica de la enfermedad sigue rodeada de incertidumbre. Los autores describen un estudio serológico realizado en la población vacuna de ocho de las nueve regiones administrativas del país (las que presentan la mayor densidad de ganado vacuno) con objeto de determinar la prevalencia y los serotipos del virus de la fiebre aftosa circulante. Tras seleccionar aleatoriamente un total de 796 cabezas de ganado y obtener de ellas muestras de suero, estas fueron analizadas en el Istituto Zooprofilattico Sperimentale della Lombardia e dell'EmiliaRomagna (IZSLER) de Brescia (Italia), que es el Laboratorio de Referencia de la Organización Mundial de Sanidad Animal y la Organización de las Naciones Unidas para la Alimentación y la Agricultura para la fiebre aftosa. Para detectar anticuerpos dirigidos específicamente contra proteínas no estructurales se empleó un ensayo inmunoenzimático (ELISA) denominado ELISA 3ABC, a lo que se agregó una serie de seis técnicas ELISA de competición concebidas para detectar y tipificar anticuerpos dirigidos contra las proteínas estructurales de los serotipos O, A,SAT 1, SAT 2, Asia 1 y C del virus de la fiebre aftosa. A tenor de los niveles detectados de anticuerpos contra proteínas no estructurales, la seroprevalencia individual era de un 35,6% (intervalo de confianza [IC] al 95%:32,2­38,9) y la seroprevalencia de rebaño era de un 62,3% (IC 95%: 53,0­71,5).La fiebre aftosa, presente en todas las divisiones administrativas ganaderas estudiadas, alcanzaba sus máximos niveles de prevalencia en las regiones meridionales, caracterizadas por tasas de pluviosidad y humedad más altas y por un mayor volumen de movimientos transfronterizos de animales. La seroprevalencia era más elevada en los ejemplares de más de cuatro años de edad, hecho que puede deberse a exposiciones reiteradas. La producción ganadera en régimen semisedentario y la trashumancia eran también factores de riesgo. Se detectaron anticuerpos contra los serotipos A, O, SAT 1 y SAT 2.

[Cost estimation of an epidemiological surveillance network for animal diseases in Central Africa: a case study of the Chad network]. / Estimation du coûét d'un réseau d'épidèmiosurveillance des maladies animales en Afrique centrale: le cas du réseau tchadien.

In sub-Saharan Africa, most epidemiological surveillance networks for animal diseases were temporarily funded by foreign aid. It should be possible for national public funds to ensure the sustainability of such decision support tools. Taking the epidemiological surveillance network for animal diseases in Chad (REPIMAT) as an example, this study aims to estimate the network's cost by identifying the various costs and expenditures for each level of intervention. The network cost was estimated on the basis of an analysis of the operational organisation of REPIMAT, additional data collected in surveys and interviews with network field workers and a market price listing for Chad. These costs were then compared with those of other epidemiological surveillance networks in West Africa. The study results indicate that REPIMAT costs account for 3% of the State budget allocated to the Ministry of Livestock. In Chad in general, as in other West African countries, fixed costs outweigh variable costs at every level of intervention. The cost of surveillance principally depends on what is needed for surveillance at the local level (monitoring stations) and at the intermediate level (official livestock sectors and regional livestock delegations) and on the cost of the necessary equipment. In African countries, the cost of surveillance per square kilometre depends on livestock density.

[Epidemiological surveillance networks for animal diseases in French-speaking West and Central Africa]. / Les réseaux d'epidémiosurveillance des maladies animales en Afrique francophone de l'Ouest et du Centre.

One of the objectives of the Pan African Programme for the Control of Epizootics (PACE) was to set up epidemiological surveillance networks in African countries. A survey based on a written questionnaire was conducted to review the technical and institutional organisation of epidemiological surveillance networks in nine French-speaking countries, including five in West Africa (Senegal, Burkina Faso, Côte d'lvoire, Togo and Guinea) and four in Central Africa (Cameroon, Central African Republic, Democratic Republic of Congo and Chad). The survey results showed that there are more similarities than differences among epidemiological surveillance networks. In general, they were found to be technically and institutionally well established. However, the two weaknesses of the majority of networks are the inadequate diagnostic capacity of laboratories and the insufficient operationality of steering committees. Epidemiological surveillance should exclusively be the domain of Veterinary Services and it is crucial for ensuring that any change in the health status of an animal population is detected rapidly. However, the networks' continuing survival after external financing ceases is generally not guaranteed because, in many cases, governments fail to fund them adequately.

[Network for epidemiologic surveillance of animal diseases in Chad]. / Le réseau d'épidémiosurveillance des maladies animales au Tchad.

An epidemiosurveillance network for diseases of animals was introduced in Chad to ensure early reporting to animal husbandry organisations should the incidence of an existing disease increase, or should an exotic disease reappear. The network also serves for the collection of information on the principal diseases of livestock. A list of eight priority diseases was drawn up with specific surveillance objectives for each disease. Information (from surveys and sampling) from all new outbreaks of the diseases under surveillance is gathered by participants in the field (officials in public service and private veterinarians) and sent to the diagnostic laboratory, which examines the findings before disseminating them to the field. The first year of operation in the field has made it possible to evaluate the feasibility of the method and to collect fundamental epidemiological information on the diseases under surveillance. The advantage of the network is the provision of a means of communication between the field and the laboratory. The network enables collection of information in a standard form, the training of field agents and the organisation of the structure of the laboratory. Persistent problems are the motivation of some participants in the field and difficulties in communication which have to be overcome in order to obtain reliable data rapidly.