Serological Epidemiology of Foot-and-mouth Disease among Sedentary Mixed-species Herds in Adamawa Region, Cameroon

Abstract

Foot-and-mouth disease (FMD) is an economically important viral disease of domestic animals and wildlife. High circulation occurs during outbreaks but little is known about the current transmission dynamics in sedentary cattle and sheep herds. To investigate on this, samples from cattle and sheep located in the Vina Division of the Adamawa region of Cameroon, during FMD outbreaks were collected. Non-Structural Protein (NSP) and antigen detecting/serotyping FMD ELISAs were used for sample screening. The NSP serological data of cattle was used to estimate transmission parameters in catalytic and reverse catalytic models. The Akaike’s Information Criteria (AIC) revealed the reverse catalytic model as the most parsimonious for the NSP serological data and was used to estimate the force of infection (FOI), the rate of waning immunity and to estimate historic periods of sustained transmission. Four serological types of FMD notably O, A, SAT 1 and SAT 2 were identified from cattle vesicular epithelia tissues. Seroprevalence findings revealed 65.14% and 15.71% FMDV antibodies in cattle and sheep respectively with highest prevalence in both populations occurring in Mbidjoro. The FOI (λ) in sedentary herds was constant; the rate of waning immunity (ω) was 0.32 meaning cattle are generally immune for 3.12 years post natural infection. The reproductive number (Rt) was 7.33, meaning approximately 87% of cattle always need to be effectively immunized to prevent outbreaks. Therefore, FMD circulates in sedentary cattle and sheep populations in the study area with four serological types detected in cattle.

Zoo-Sanitary Situation Assessment, an Initial Step in Country Disease Prioritization Process: Systematic Review and Meta-Analysis from 2000 to 2020 in Cameroon

“…Five serotypes of the virus were: A, O, SAT1, SAT2, and SAT3 ( Table S21 ). Overall, low pooled prevalence was significantly ( p = 0.001) observed with pigs: 4.4% [95% CI (3.1–6.3%)] and sheep: 8.1% [95% CI (3.6–17.4%)] compared to cattle: 33.5% [95% CI (2.2–92.0%)] ( Figure 6 ) [ 36 , 37 , 38 , 39 , 40 , 41 , 42 ]. Subgroup analysis for the Adamawa region gave a pooled regional prevalence of 34.8% [95% CI (8.6–75.1)].…”

Foot-and-mouth disease in Cameroon: A systematic review to support its progressive control

“…From published technical documents and articles, the highest number of serotypes was recorded in the Far-North region (O, A, SAT1, 2, 3) [8] (Table 1). The North, Adamawa and North-West regions have the same number of serotypes (O, A, SAT 1, SAT 2) [3,4,9,12,14] . The other regions such as Littoral and Center have low serotype diversity, while for the South-West and South regions there is no information on the circulating serotypes (Table 1).…”

“…Cattle O [20] 1981 to 1984 Cattle, Pigs O [20] 1985 to 1987 Cattle, Pigs, Goats, sheep A, SAT3 [20] 1988 Cattle, Pigs O, A, SAT2,SAT3 [20] 1989 Cattle O, A [14] 1996 Cattle O,A,SAT2 [14] 1998 Cattle SAT2 [14] 2004 Cattle O, A [3] 2005 Cattle O,A,SAT1, SAT2 [14] 2006 Cattle O,A,SAT1, SAT2, SAT3 [4,14] 2014 Cattle O,A,SAT1,SAT2,SAT3 [8] 2015 Cattle O,A,SAT1,SAT2,SAT3 [14,26] 2018 Cattle O,A,SAT2 [5,12] 2019 Cattle, Sheep, Goats O, A, SAT1,SAT2 [6,9,14] 2020 Cattle SAT1 [7] Risk-based identification findings: The transmission life cycle of FMD has been studied and remains complex for endemic settings. Some aspects of the foot-and-mouth disease virus (FMDV) life cycle such as its persistence in the environment, the occurrence of subclinical animals (domestic and wild) and the possibility of transmission from small ruminants to cattle remain subjects for debate.…”

“…Some of these practices are an exchange of bulls for reproduction purposes, allowing sick animals to mix with non-sick counterparts, transhumance towards FMD wild reservoir sites with buffaloes, antelopes, warthogs, and mixed livestock farming (whereby herders mix herds of different susceptible animal species such as goats, sheep, but rarely pigs with their cattle). Studies conducted in the North and Adamawa reported serotype O in small ruminants (sheep and goats) [9] . Additionally, the study in the North identified that herders who practised grazing of small ruminants with other animal species reported high FMD contamination.…”

“…In 2019, SAT1 topotype X was reported for the first time in bovine epithelial tissues from North Cameroon [6,7] . Indeed, serological epidemiological studies have established the occurrence of five serotypes-O, A, SAT1, SAT 2, SAT 3 [8,9] . As international borders remain permeable without strict veterinary checkpoints to identify, isolate and prevent sick animals from entering the country, the risk of incursions of FMD viruses is very obvious as shown in studies conducted at border levels between Cameroon and neighboring countries such as Chad, Central African Republic (CAR), and Nigeria [7,10,14] .…”