Neglected zoonotic diseases and cross-border livestock movements in northern Côte d'Ivoire : towards local and regional integrated control

Background: Neglected zoonotic diseases (NZDs) are less prioritized in Africa, which is in contrast to their impacts on human and animal health and livestock production. Brucellosis, Q fever and Rift Valley fever (RVF) are among the most common NZDs that occur in Western Africa. Cross-border livestock movements are frequent in Africa given the centuries-old practice of mobile pastoralism. They are described to be associated with the spread of “highly contagious epidemic animal diseases with significant economic and food security concerns, known as Transboundary Animal Diseases -TADs”, which include NZDs of interest in this PhD thesis. Although movements are central to livestock production in the Economic Community of West African States (ECOWAS), they are mostly uncontrolled. Additionally, veterinary services of the neighboring countries have hardly collaborated with respect to cross-border control of diseases. Currently the epidemiology as well as the public health and economic importance of TADs in general and NZDs in particular remain unknown in the region. The aim of this research was to generate epidemiological data on NZDs and TADs in order to assess their economic impact as well as to design appropriate regional control strategies.
Methods: Multi-stage cross-sectional cluster surveys in livestock and humans between 2012 and 2014 in a random selection of 63 villages and a sample of 633 cattle, 622 small ruminants and about 100 people were conducted. Sera were tested with the Rose Bengal Plate Test (RBPT); indirect ELISAs for Brucella spp., B. ovis and C. burnetii; and a competitive ELISA for B. melitensis and RVF. Then questionnaires were administered regarding NZD risk factors. The economic impact of brucellosis on milk, meat and hide productions were calculated for Côte d’Ivoire using a stochastic projection matrix model which simulated the demographic growth and compared cattle productions with and without brucellosis. Regarding cross-border control of livestock movements and diseases, thirteen focus group discussions with mobile pastoralists, agropastoralists and farmers as well as eleven key-informant interviews with animal health professionals and livestock movement supporting agencies were conducted. Additionally, cross-sectional serological surveys on brucellosis and Q fever in humans (n = 76), cattle, sheep and goats (n = 537) in slaughterhouses along pastoral corridors in northern Côte d’Ivoire and Abidjan were also performed.
Main results: The seroprevalence of Brucella spp. adjusted for clustering was 4.6% in cattle, 0% in sheep and goats and 5.3% in humans. In cattle, age, mixed-herding with other livestock species and having joint hygromas were significant predictors. The seroprevalence of Q fever was 13.9%, 9.4% and 12.4% in cattle, sheep and goats, respectively. The seroprevalence of RVF was 3.9% in cattle, 2.4% in sheep and 0% in goats. Abortion was a significant predictor of seropositivity in ewes. About 4% of the cattle had antibodies against both Q fever and RVF. The Ivorian cattle population was simulated and estimated to be about 1,885,123 and 1,906,961 with and without the disease in 2015, respectively. An overall intrinsic growth rate of 1.8% and 17.4% meat offtake rate were derived. The cumulated net present cost attributable to brucellosis infection was estimated at FCFA 14,455 x 106 (95% CI: 6,278–22,906). The incremental live cattle asset value was projected to FCFA 3,826 x 106 (95% CI: 1–7,6) in 2015. Regarding cross-border livestock mobility, key-informant interviews and group discussions identified almost 30,000 cattle from 200 mobile pastoralists involved each year in uncontrolled cross-border movements between Mali, Côte d’Ivoire and Burkina Faso. TADs such as Contagious Bovine Pleuropneumonia (CBPP), Foot-and-Mouth Disease (FMD), tuberculosis, lumpy skin disease, pasteurellosis, brucellosis and Blackleg were ranked to be the most important diseases in cattle whereas “peste des petits ruminants” (PPR) was the only disease reported in sheep and goats. Lack of veterinary staff and transportation means in veterinary services, poor cross-border veterinary collaboration and harmonization of disease control activities were the main constraints to controlling their spread. The study identified over-arching themes regarding the challenges and needs for cross-border control of TADs and movements and established a program for the harmonization of disease control activities in the three countries.
Conclusions: Our results provide updated epidemiological and economic descriptions of NZDs in Côte d’Ivoire. The research identified key diseases, areas of increased livestock movements, corridors/routes, and needs for cross-border control of movements and diseases in the Sudano-Guinean savanna. Cross-border collaboration should be promoted for the implementation of an effective and durable control. There is an urgent need for cost-effectiveness studies to complement our economic impact estimations as well as studies to better explore and understand the added value of cross-border cross-sectoral collaboration and coordination regarding feasible movement and disease control.