Brucella is gram-negative bacteria that are pathogenic to humans and a variety of livestock animals and wildlife. The genus Brucella has six recognized species on the basis of host specificity. While all six species occur at least sporadically in the United States and sub-Sahara Africa, the greatest economic impact resulted from bovine brucellosis caused by B. abortus. Infection decreases reproductive efficiency, mainly by abortion. The disease has elicited Brucellosis, a zoonotic disease of public health importance; this animal disease has been eradicated in many developed countries [1]. Brucellosis remains one of the seven zoonotic diseases declared by the World Health Organization [2] but has been “neglected”. The disease has a great impact on both animal and human health as well as tremendous socio-economic impact in developing countries where people’s income relies largely on livestock breeding and dairy products [3]. Brucellosis is endemic in livestock in most countries of Africa including Nigeria [4] and is an established endemic disease among Nomadic herdsmen and cattle slaughter houses in sub-Saharan Africa and Nigeria [5] [6].

Several species of Brucella that are important to public health exist amongst which B. abortus and B. melitensis are more virulent for humans than B. suis and B. canis although serious complications can occur with any species of Brucella [7]. Humans are infected either by direct contact with blood, placenta or uterine secretions of infected animals, through breaks in the skin, by inhalation or by ingestion of unpasteurized milk and other dairy products [8]. It is known that unpasteurized milk is sold in several parts of Nigeria. Brucellosis is an occupational hazard to individuals engaged in certain professions such as abattoir workers, veterinarians, livestock farmers and herdsmen [9].

This study focuses on abattoir workers in three abattoirs and Nomadic herdsmen raising camp in Akwa Ibom State, Nigeria. This is because brucellosis is a recognized occupational hazard which is rarely diagnosed in most health facilities in the country, and is yet to be included in the Integrated Disease Surveillance and Response (IDSR) system—public health surveillance and response system for priority diseases [10] [11]. Very few studies have been done on the prevalence of brucellosis among these occupational group persons in Nigeria [12].

➢ The main objective of this study was to determine the sero-prevalence of Brucellosis in Akwa Ibom State, Nigeria.

➢ To determine the risk factors associated with human brucellosis among abattoir workers, livestock farmers and herdsmen.

➢ To compare the diagnostic performance of standard tube agglutination tests: (SAT¹⁶⁰) and ELISA (IgG, IgM) kits.

➢ To proffer the possible measures in controlling the diseases outbreak in the study area.

A total of 228 subjects participated in the study with brucellosis seroprevalence of 30.8% (n = 70). More male participated in the study with a frequency of about 24.6% of whom 7.92% fall within the age group of 20 to 30, followed by 31 - 35 years (5.72%) and 36 - 45 years (3.52%) and least affected were those in the age groups above 46 years (Table 1). Approximately 21.54% of the subjects had attained formal education either at Quranic level, primary and secondary or tertiary. Majority (9.68%) had acquired Quranic education, 7.48% primary and 0.88% had tertiary training. Nearly 9.24% had never acquired any form of education with majority of the participants being Muslims (Table 2). Headache,

muscle aches, malaise, chills and fatigue were the most common clinical signs and symptoms experienced by about 30% among the participants (Figure 2). In the distribution of Brucella antibodies ELISA diagnostic kits showed high sensitivity with the prevalence rate of 18.04% (n = 41) followed by SAT (12.76%) (Table 5). Workers within the ages of 20 to 30 showed significant at bivariate analysis dues to long years of occupational exposure to the animal (Table 1).

This research highlights the sero-prevalence (30.8%) of brucellosis among Herdsmen, Abattoir and Livestock workers in an urban set up of Akwa Ibom State, Nigeria (see Table 3). This is in agreement with the reported by Pappas et al. [5] with 35% sero-prevalence of brucella bacteria in Tunisia and 34.2% in Iraq [1]. The study in Iraq mainly looked for the disease among febrile patients who were principally abattoir workers and herdsmen. This could be explained probably by the high incidence and unstandardized control protocols of the disease in livestock as well as inability to appropriately manage brucellosis in humans which is contrary to practices in developed countries. Among the various categories of the subjects that were screened, nomadic herdsmen had the highest sero-positivity rate of 31 (13.6%) followed by abattoirs workers 23 (10.1%) (see Table 1). Similar findings have been documented from studies done in South West Nigeria, Tanzania and Egypt [14] [15] [16] , suggesting that they are more at risk probably because of their close contacts with blood and tissues of infected animals. In this study, brucellosis infection was present across all the genders and educational status, which corresponds with study by Mantur et al. [4].

In addition, males appeared to be more at risk of infection with brucellosis 26.4% (Table 4). However, it should be noted that cattle raising and butchering is a male-dominated activity and this may have accounted for this finding. Workers with tertiary education working in the abattoir seem to be less at risk of infection. This category of workers will usually have become managers with many apprentices working under them and are rarely responsible for the direct rearing and slaughtering but usually serve in supervisory or advisory capacities [17].

In the present study, the prevalence rate of brucellosis was 30.8% and standard tube agglutination test was positive in 12.76% (29/228) at a titre level of 1:160 while ELISA rapid test was 18.04% (41/228) of the subjects (see Table 5). The finding of the present study indicates a low specificity for SAT¹⁶⁰. Similar results have been reported in other studies from endemic areas, where there may be high levels of specific and cross reacting antibodies [18].

Enzyme-linked immunosorbent assay ELISA is based on detection of IgG and IgM antibodies which appear in detectable titres as early as the second day of illness. In many circumstances, especially among partially treated cases presenting to health facilities, combining SAT¹⁶⁰ and ELISA may reduce the diagnostic difficulty in brucellosis. The ELISA offers an additional advantage among serologic diagnostic tests for brucellosis in that the test strips do not require an ELISA reader for evaluation. Also, only minimal operator training is required. Nevertheless, the higher cost of the test in comparison with the SAT¹⁶⁰, as well as cold-storage requirements for test reagents, are additional impediments in using this test in developing countries.

In the present study, we conclude that ELISA is a practical alternative to SAT¹⁶⁰ in the diagnosis of Brucella infection on account of its increased sensitivity, early detection of cases, and ease of procedure with minimal infrastructure and availability of results on the same day. However, a larger prospective study would be required to fully evaluate the usefulness of this test in countries endemic to Brucella disease.

Clinical presentation of the illness among the study participants was similar although fatigue, chills and headache were the most clinical symptoms experienced by Brucella positive cases. Indiscriminate clinical signs are a common phenomenon that has been reported from other studies [15].

The sero-prevalence of human brucellosis among abattoir workers in Akwa Ibom State was high, with Nomadic herdsmen having the highest sero-positivity. Rearing of animals and handling aborted fetuses couple with occupational exposure of over 6 years were important factors associated with sero-positivity for brucellosis. Health education is at the risks that herdsmen and abattoir workers face from contracting zoonoses and the consistent use of personal protective equipment by Nomadic and abattior workers will go a very long way in preventing infection in the population at risk. Based on the findings of this study, the following recommendations were made to the relevant authorities. Government at all levels should organize public enlightenment campaigns aimed at highlighting the importance of zoonoses including brucellosis among Nomadic herdsmen, abattoir and livestock workers who should also be encouraged to go for brucellosis screening every 3 years. Abattoir workers should be discouraged from eating raw meat and educated on adherence to safe animal-product handling practices. A continuous sero-survey should be considered at regular intervals as a monitoring tool for the prevalence of human brucellosis in Nigeria.

The screening was carried out using human IgG and IgM ELISA kits specific for B. melitensis and the results were correlated with those of the SAT (1:160) test. The reagents in the kit were reconstituted and the test procedure was carried out according to manufacturers’ instructions. Individuals were considered as positive based on a positive SAT (1:160) or ELISA result.

The authors declare no conflicts of interest regarding the publication of this paper.

Owowo, E.E., Antia, U.E., Christopher, M.A. and Okon, I.E. (2019) Sero-Prevalence of Brucellosis among Nomadic Herdsmen, Abattoir and Livestock Workers in Niger-Delta Region, Nigeria. Journal of Biosciences and Medicines, 7, 32-41. https://doi.org/10.4236/jbm.2019.710003