Introduction

Within pastoral and agro-pastoral systems, camelids made significant socio-economic contributions. The main sources of income in arid and semi-arid regions of northeast, east, south, and southeast Ethiopia are the production of milk, meat, and hides, as well as transportation, draught power, and pharmaceuticals (1, 2). Nevertheless, camels are more vulnerable to various infectious and non-infectious diseases, as well as ailments related to reproduction and the desert, due to increased stress caused by droughts and desert conditions. The primary cause impeding production and productivity is camel brucellosis (3). Russia published the first report of brucellosis in camels in 1931 [4]. Brucella abortus and Brucella melitensi are the primary cause of brucellosis in camels. Although each brucella species is typically linked to a specific host, other species can also be infected, especially if they are kept near each other.  Different findings state that milk, aborted fetal samples, and vaginal swabs from suspected camels are the most common sources of isolation for both species of brucella (5, 6).

Brucellosis is a serious disease that affects cattle, sheep, goat, and camel populations in sub-Saharan Africa. It is especially harmful to pastoralists and agro-pastoral systems, where human infection is common (7). The first case of camel brucellosis in Ethiopia was reported from the Sidamo, Harar, and Tigray regions, with a seroprevalence of 4.4% (8). Furthermore, a study on camel brucellosis was conducted in the lowlands of Borena, where the seroprevalence was 1.8% (9). Moreover, reports of brucellosis in camels from various pastoral areas have been made; the incidence varies considerably, ranging from 0.73 to 11.9% for the Rose Bengal plate test (RBPT) and from 0.53 to 9.6% for the Complement Fixation Test (CFT) (10).

The differences in animal husbandry and management techniques used by pastoral and agricultural societies are thought to cause this discrepancy in the seroprevalence of camel brucellosis (11). The size of a herd, husbandry practices, the use of maternity pens, the lack of vaccination, and common grazing and watering with mixed ruminant animals are among the management factors that influence the transmission of Brucella species, which can enter hosts through ingestion, inhalation, sexual contact, and broken skin (12). The presence of Erythritol in fetal tissues and the uterus causes Brucella species to exhibit a preferential tissue tropism for female reproductive organs. The disease is characterized by placentitis, but can also cause epididymitis and orchitis in male camels. Symptoms of the disease include late-term abortions, weak calves, stillbirths, and infertility (13, 14).

According to the World Health Organization, the Food and Agriculture Organization, and World Organization for Animal Health, the third most significant zoonotic disease worldwide is brucellosis (15). The likelihood of contracting the disease has been increased for those who come in contact with the discharge of sick animals, such as farmers, butchers, and veterinary staff (16). Among the most common illnesses in the world, brucellosis has major negative effects on the economy (17). This disease is causing large reproductive losses in sexually mature animals (18), impeding the free movement of animals, restricting the trade in cattle, and delaying exporting (17, 18). In camel production pastoral areas in Ethiopia, brucellosis is one of the diseases that must be reported when there are reproductive problems (such as delayed puberty and calving age, increased calving interval, infertility, and decreasing milk yield) (17).

Brucellosis is a zoonotic disease that can affect humans causing disastrous health and economic effects (19). It is well known that pastoral community life is dependent on livestock and their products. Significantly, the role of camels in family growth is very high in pastoral areas. Camels can survive in harsh environments, but various unknown diseases have hindered their production. Pastoralists are in close contact with their animals, and consumption of raw milk and handling of aborted materials is common making them more exposed to the risk of infection in the study area. This study aimed to evaluate the seroprevalence and risk factors related to brucellosis in dromedary camels and the knowledge, attitudes, and actions of camel owners regarding brucellosis at the human-animal interface that could endanger humans in the study area.

Material and Methods

Description of the study area

The study was conducted in the Lega Hida district in East Bale Zone, Oromia Region, Southeastern Ethiopia (figure 1; figure 2). It is located between 6^o 0 ’0’’ and 8^o3 0’ 0” N latitude, and 40^o30’0” and 41^o40’0” E longitude, about 108 km from the capital of East Bale Zone and 528 Km from the capital of Ethiopia, Addis Ababa. It is bordered by Somali Regional State to the east, East and West Hararge Zone to the north, Gololcha to the west, and Sawena district to the south. The area experiences a bimodal rainfall occurring from March to the end of June and a small rainy season Usually from September to late October. The mean annual rainfall ranges from 500 to 800 mm and temperatures from 25°C and 28°C are recorded (20). The production system of the district is pastoralism. The majority of the communities in this district get income from livestock and livestock products. This district has 27 villages. Among this, the study was conducted in five villages namely Adele, Goni, Wanjisa, Hida hunda, and korba. The livestock population in the area comprises about 394,368 goats, 39,159 sheep, 293,413 cattle, 21,116 donkeys, 11,520 mules, three horses, 50,058 camels, and 25,560 poultry. Although camels can survive in a harsh environment, various unknown diseases in the region are the main obstacle to getting enough production of camels (Agriculture Office, 2023 (unpublished)). 

Study population and animals

Dromedary camels raised under extensive pastoral production, allowing for free browsing in Lega Hida, made up the research population. Camels above six months of age, were not vaccinated against brucella species and both sexes were considered. The total camel population of the district is estimated to be about 50,058. Camels’ age was classified into ≤4 yrs, 4–10 yrs, and >10 yrs as young, adult, and old age groups, respectively, according to Fekadu et al. (21).

Study Design

A cross-sectional study was conducted using serological tests. The RBPT and the indirect enzyme-linked immunosorbent assay (ELISA) test were used to determine the seroprevalence of brucellosis in dromedary camels. Data were collected to determine the risk factors associated with the seropositive animals in the study area. Zone and district were selected based on the camel population, while the study villages were randomly selected.  

Sample size determination and sampling technique

The sample size was determined based on the method described in Thrusfield (22). Since the seroprevalence of brucellosis in dromedary camels in the Lega Hida district had not previously been reported, the calculation took into account an absolute precision of 5% and a 95% confidence interval. The result was 50% expected seroprevalence (Pexp). The minimum number of camels required was computed using the following formula:

n = Z²Pexp (1-Pexp)]                                                                         n = (1.96)²(0.5(1-0.5) = 384

              d²                                                                                                          0.05

Where;

 n = required sample size

Pexp = Expected prevalence = 0.5

d=margin of error = 0.05

Z= 95% CI =1.96

The sample size increased to 404 (5%) to increase the chance of observation and estimate the wide distribution of brucellosis in the study area. Simple random sampling was used to choose the study animals. The minimum sample size needed to determine the prevalence was calculated to be 384.

Questionnaire survey

Before the interview began, the respondents verbally agreed and were informed of the survey's goals. Questionnaires were prepared first in English language and translated into the local language Afaan Oromoo. The questionnaire centered on knowledge of zoonotic diseases, attitudes toward the danger of contracting brucellosis and preventing exposure to animal birth products, and strategies for mitigating the risks of contracting diseases from animal products.

Laboratory examination

5-10 blood samples were collected from the jugular vein of camels. The collected blood samples were allowed to clot at room temperature. Then, the serum was separated and decanted into cryovial 1.7mL tubes.