Seroprevalence of brucellosis and associated risk factors among abattoir workers in Bauchi State, Nigeria

Introduction Brucellosis is a reemerging and neglected zoonotic disease. It is an occupational bio-hazard and a public health problem. The objective of the study was to determine the seroprevalence of brucellosis and its risk factors among abattoir workers in Bauchi state. Methods A cross-sectional study was conducted in the three senatorial district abattoirs of Bauchi State. Abattoir workers (n=284) were selected by stratified random sampling. Data were collected using an adapted questionnaire. Serum samples collected, were screened for brucellosis with Rose Bengal Plate Test (RBPT), tested with Enzyme Linked Immunosorbent Assay (ELISA). Seropositive participants were positive for both RBPT and ELISA. Data were described in proportions and analyzed using bivariate and multivariate analysis. Results Participants were all male, age range: 18-70 years (mean 35 ±13 years). Ninety-five participants were seropositive (seroprevalence 33.5%) after laboratory testing. Following bivariate analysis, using personal protective equipment (PPE) [OR: 0.5 CI95%=0.3>OR: 0.5 CI95%=0.3-0.9] was significantly protective against brucellosis. Slaughtering of animals (OR: 2.19 CI95%= 1.2-3.7), assisting in animal parturition (OR: 2.25 CI95%= 1.3-3.7), working with an open cut/wound (OR:2.1 CI95%= 1.1-3.9) and eating while working in the abattoir [OR:2.4 CI95%= 1.1>OR:2.4 CI95%= 1.1-4.9] were risks of brucellosis. Multivariate analysis showed that slaughtering of animals: Adjusted Odds-Ratio (AOR) = 1.92; CI95% = 1.03 - 3.59) and assisting in animal parturition (AOR = 2.43; CI95% = 1.40 - 4.23) remained significantly associated with brucellosis. Conclusion Seroprevalence of brucellosis among abattoir workers in Bauchi state is high. Workers should use PPEs and animal parturitions should be handled by trained personnel alone.


Introduction
Brucellosis is one of the most common and important global zoonotic disease, [1,2] with reported worldwide incidence of human brucellosis at >200 per 100,000 population [3]. It is caused by a fastidious, intracellular, non-spore forming, non-motile, non-encapsulated, gram negative coccobacillus bacterium of the genus Brucella [4]. Brucellosis is listed by the World Health Organization (WHO) as a "neglected" zoonotic. The disease has a great impact on animal and human health as well as socio-economic impact in developing countries [5]. Due to abortion, lower milk production and reduced fertility in livestock and serious health problem in human beings [6]. Animals are the natural hosts of the Brucella organisms and are reservoirs for human infection. Brucellosis incidents have been reported in terrestrial and marine mammals also in domestic animals [7]. Humans acquire the infection through contaminated environments/tissue, foodborne transmissions, inhalation. Occupational exposure usually results from direct contact with infected animals [6] and animal product: blood, placenta or uterine secretions of infected animals, the bacteria gains access through breaks in the skin and mucosa [5,6]. This involves abattoir workers, farm laborer, animal keepers, butchers, veterinarians and laboratory workers, where Brucella melitensis and B. suis species are more virulent for humans than B. abortus and B. canis [6,8].
Brucellosis in humans is a systemic disease characterized by sever/acute, insidious onset of continued, intermittent, undulant or irregular fever of variable duration, headache, profuse sweating, chills, weakness, generalized aching and joint pain [9]. Relapses hypersensitivity reactions [10] are common; focal lesions occur in bones, joints, genitourinary tract and other sites. Its clinical picture is not specific in animals or humans and diagnosis needs to be supported by laboratory tests. A history of recent exposure to a known or probable source of Brucella spp, occupational exposure or residence in a high infection prevalence is a probable case of brucellosis.
Differential diagnosis can be achieved by demonstration of by a validated serological method of Brucella antigen in blood (seroprevalence) or other tissue sample [6]. Brucellosis is endemic in Nigeria, resulting in massive economic losses of man-hours in infected people [11]. There are major gaps in epidemiological data, diagnostics, surveillance and control. Information essential for evaluation of zoonotic potential and for establishment of control measures is still lacking [12]. Brucellosis was found to be endemic among cattle in the three senatorial zones of Bauchi State Nigeria [13]. This study aimed to determine the seroprevalence and exposure factors associated with human brucellosis among abattoir workers in Bauchi State, Nigeria, so that policymakers and stakeholders know the extent and factors associated with the problem and can make informed decisions in the control of brucellosis in Nigeria.  (Table 3). In logistic regression model following factors that were  (Table 4).

Discussion
The findings from this study show that the seroprevalence of brucellosis among abattoir workers in Bauchi state is high. The Azare abattoir which has a livestock market situated close to it and attracted traders and animal owners from other communities from within and outside the state including Yobe and Kano State, had the most seropositive participants. The age groups most at risk was observed to be the younger age group of workers, these were mostly apprentices of much older butchers, they did most of the physical work requiring direct contact with the animal carcasses. Slaughtering of animals in northern Nigeria is a male dominated job. This is evident where all the workers that participated in the study were men. Among the various categories of abattoir workers that we screened, workers who participated in slaughtering animals and selling meat at the markets and stalls had the highest seropositivity rate. Factors associated with seropositivity include: slaughtering animals in the abattoirs, assisting in animal parturition, working in the abattoir while having an open cut or wound and eating while working in the abattoir.
We also observed that workers who used PPEs like protective hand and foot wear while working in the abattoir were at least twice less likely to become seropositive with the brucella organism. This study found that seropositivity to the brucella organism increased with ascending number of years of work or employment in the abattoirs.
Seropositivity was observed to increase steadily with increasing number of years of employment or service in the abattoir. Participants who have been employed for between 11-20 years and more than 20 years showed the highest numbers of seropositivity to the brucella organism.

The same was observed in another study carried out in 2010 in
Abuja [15], where it was also observed that working in the abattoir for more than five years was a significant variable to seropositivity to human brucellosis. The age group 21-30 years had the most seropositive in the study, this may be owing to the fact that these set of people were involved in most tasks in the abattoirs that bring them in contact with animals, meat, blood and other infectious products.
Equally the older workers who were more likely to be involved in supervisory tasks in the abattoir were observed to be less at risk of brucellosis. The findings in this study indicate that among the various occupational groups found in the abattoir, the butchers who slaughtered animals and also sold meat to customers at stalls and shops were most likely to be seropositive. This might be because these jobs carried a higher risk to physical injury from cuts and other workrelated hazards and they had more contact with animals and animal tissue. Veterinarians and meat inspectors were observed to be less at risk and were more likely to use personal protective equipment (PPE).
Studies in Ethiopia also revealed that because veterinarians and workers with post-secondary education background have considerable knowledge about the diseases during their professional training and also have good amount of practical knowledge through their experiences, they were less at risk of human brucellosis [17].
Bivariate, we found that worker involved in slaughtering animals at the abattoir were two times more likely to develop human brucellosis (p=0.003). This is consistent with the reports of studies done in Tanzania indicating significant risk among workers involved in cutting animal throats at the abattoirs [18].
People working in the abattoir while having an open cut or a wound were twice as likely to develop seropositivity to brucellosis (p=0.02).
Inoculation through cuts and abrasions in the skin is one of the modes of transmission of brucellosis [6]. Other studies have reported similar findings where persons with bruises or cuts were more likely to be infected [15]. Workers assisting in animal parturition were found to be twice more likely to be seropositive for brucellosis (p=0.001).
Farmers (and butchers) in Africa have been known to attempt assisting in parturition, handling retained placentas and trading in gravid uteruses [19]. Infected fetuses and placenta have been observed to carry high doses of infective organisms [6] direct contact with fetuses and uterine contents from livestock that have been shown to a significant risk in other studies [20,21] . Workers were observed to be less likely to be seropositive to brucellosis when they used Personal Protective Equipment (PPEs) like hand and foot wear (0.02) same was observed in other studies where use of PPEs was found to be a protective factor against brucellosis among slaughter house workers in Iran [22] and Tanzania [18]. In a study in Cameroon, all Brucella IgG seropositive respondents did not use of personal protective equipment (such as gloves) during work [21]. In another study it was reported that the constant use of full protective gear among few participants was most protective [23]. Although other studies associated eating raw or uncooked meat, unpasteurized milk and milk products with brucellosis [15,23] we found that there was a two-fold likelihood of seropositivity where participants admitted to eating food or drinks while working in the abattoir premises (p=0.02). Rifampicin Tablets 600 mg [6].
What is known about this topic  Brucellosis is a zoonotic disease that poses great risk to animal handlers and abattoir workers especially in sub-

Competing interests
The authors declare no competing interests.