Document Type : Original Article
Authors
Faculty of Veterinary Medicine, Hawassa University, Hawassa, Ethiopia
Abstract
Brucellosis is a communicable zoonotic disease that is endemic in Eastern Africa and other countries, humans contracted this infection from diseased animals. This study aimed to evaluate the seroprevalence and risk factors associated with brucellosis in dromedary camels and the knowledge, attitude, and practice of camel owners regarding brucellosis at the human-animal interface that could endanger humans in the study area. A cross-sectional study determined the seroprevalence of camel brucellosis in 404 camels. A questionnaire survey involving 120 participants was also conducted to assess the knowledge, attitude, and practice of camel owners regarding the disease. The seroprevalence of camel brucellosis was estimated as 6% by the Rose Bengal plate test and 0.5% (95% CI: 0.1-1.8) by indirect enzyme-linked immunosorbent assay (iELISA). Pastoralists are in close contact with their animals, and the consumption of raw milk and handling of abortive material is common, which exposes them to a higher risk of infection. The questionnaire survey indicated that about 40% of respondents had previous knowledge about the disease. Almost, 17% and 40% knew that the disease can be transmitted from camel to humans and between camels, respectively. About 67.5% of the respondents disposed of aborted fetuses and placenta in the open field and 86.7% of the respondents consumed raw milk. This indicates that an awareness campaign is important to equip pastoral communities in the study areas with knowledge about the disease and change their malpractice to protect themselves from brucellosis. Qualitative and quantitative research methods were used in the study. The present study revealed a low seroprevalence (0.5%). Although the seropositive animals in this study appeared to be healthy, the results indicated that the disease may manifest as a carrier and adversely affect productivity and public health.
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Main Subjects
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 6o 0 ’0’’ and 8o3 0’ 0” N latitude, and 40o30’0” and 41o40’0” 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.