Epidemiological studies of brucellosis, campylobacteriosis and trichomonosis, and other factors affecting calving rate in cattle herds in northern Nigeria

Abstract

Livestock production, of which cattle production is a major component, plays a key role in the socio-economic development of Nigeria, with 70-80% of the nation’s population of over 150 million engaged in agriculture and the livestock industry as their major occupation. Cattle production provides essential food products – meat, milk, and other dairy products, animal power, fuel, transport and organic manure for arable farming. However, the productivity and reproductive performance of cattle in Nigeria is generally low due to many factors, including a number of infectious reproductive diseases resulting in decreased calving percentage, infertility, abortion and decreased milk production. Brucellosis is one of the most important reproductive diseases and widespread zoonosis in the world and previous studies have indicated an increase in its occurrence in cattle in Nigeria. In addition, bovine campylobacteriosis and trichomonosis are widespread diseases associated with bovine infertility worldwide. However, there is little recent or reliable information on the prevalence of these important diseases in Nigeria and their effect on reproductive performance. Most studies have used nonrepresentative samples, small sample sizes and relatively non-specific diagnostic tests. Few studies have been conducted on bovine campylobacteriosis and trichomonosis in Nigeria and none on the concurrence of brucellosis and campylobacteriosis. Therefore, a large crosssectional study covering Adamawa, Kaduna and Kano states of northern Nigeria was designed. A multistage random cluster sampling strategy was used to sample 4,745 cattle from 271 herds, including diverse production systems. The objectives of the study were to estimate, at the animal and herd level, the seroprevalence of brucellosis in adult cattle, the prevalence of bovine genital campylobacteriosis and trichomonosis in bulls and the association between the three diseases. In addition, the study aimed to identify herd-level managemental and environmental risk factors for each of the diseases, as well as risk factors for within-herd seroprevalence of brucellosis. Further objectives were to determine the reproductive efficiency and occurrence of reproductive disorders in the herds, and to estimate the effect of the three infectious diseases, as well as other factors, on calving rate. Serum samples were tested for antibodies to Brucella using the Rose-Bengal plateagglutination test (RBPT) and positives were confirmed using a competitive enzyme-linked immunosorbent assay (c-ELISA). Thirty-seven percent of all animals were RBPT positive, and after confirmation with c-ELISA the overall true animal-level prevalence, adjusted for test sensitivity and specificity and for sampling weights and clustering in the complex survey design, was 26.3% (95% CI, 22.1%-31.0%). Of the herds sampled, 210 (77.5%; 95% CI, 68.6%-84.5%) had at least one animal positive to both tests; this did not differ significantly between states (P = 0.538). A significantly higher seroprevalence of brucellosis was found in males than in females (P < 0.001), in non-pregnant than in pregnant females (P < 0.001), and in cattle >7 years than in cattle <4 years of age (P < 0.001). Seroprevalence was highest in the pastoral management system (45.1%) while the commercial system had the lowest seroprevalence with 15.9% (P < 0.001). Preputial samples of 602 bulls from 250 herds were tested for Campylobacter fetus and Tritrichomonas foetus using culture and identification. The estimated true animal-level prevalence of C. fetus infection in bulls was 16.4% (95% CI: 13.0%-20.7%), of which 18.5% was C. f. fetus and 81.5% was C. f. venerealis. Of the latter, 92% were C. f. venerealis biovar intermedius, the major aetiology of bovine genital campylobacteriosis. A higher prevalence was found in bulls >7 years old (33.4%) than in bulls 4-5 years old (13.6%) (P = 0.018). Prevalence was highest in the Gudali breed (28.8%) and in pastoral herds (43.5%). There was a strong positive association between the presence of campylobacteriosis and brucellosis, both within bulls (OR = 8.3, 95% CI: 5.2-13.4) and within herds (OR = 16, 95% CI: 3.8-68) (P < 0.0001). All the samples tested for trichomonosis using different isolation methods were negative. Multilevel logistic regression models were used to identify herd-level risk factors for brucellosis and campylobacteriosis. The odds of both Brucella seropositivity and C. fetus infection increased significantly with the presence of small ruminants (sheep and/or goats) on the same farm and with the introduction of animals to the farm without quarantine. In addition, Brucella seropositivity was positively associated with larger herd size, with the pastoral management system and with the presence of a crush or improvised chute on the farm, while regular or occasional gynaecological examination was associated with reduced odds of seropositivity. Initial purchase of stock from a market, regular or occasional gynaecological examination, failure to practice regular or occasional herd prophylactic measures and high rainfall were associated with increased odds of C. fetus infection. A zeroinflated Poisson model showed that the presence of small ruminants, the introduction of animals without quarantine, and borrowing or sharing of breeding bulls were associated with a higher within-herd seroprevalence of brucellosis within infected herds, while routine provision of mineral supplementation was associated with a lower within-herd seroprevalence.