Brucellosis is a bacterial zoonotic disease caused by the genus Brucella that causes reproductive problems such as abortion, retained fetal membranes, and the birth of weak offspring, as well as orchitis and epididymitis in male animals, which is frequently followed by sterility (1). There are 12 known Brucella species that cause brucellosis at this time (2) and six of them, are known to be pathogenic to humans: B. abortus, B. canis, B. inopinata, B. melitensis, B. pinnipedialis, and B. suis (2, 3). This taxonomic classification is primarily based on differences in host preference and pathogenicity that can be attributed to different proteomes, as demonstrated by specific outer-membrane protein markers (4, 5). Around the world, Brucella species that infect both humans and animals are frequently discovered in the interface of the human-animal ecosystem, where strong interactions exist between people, livestock, and wildlife in the same area (6, 7).

Brucella abortus causes abortion, stillbirth, and weak calves in cattle, with abortions typically occurring during the third trimester of pregnancy. B. melitensis is the most common species in developing countries in small ruminants and is linked to clinically visible diseases in humans (8). B. melitensis can cause abortion, retained placenta, orchitis, and epididymitis in goats. Abortions in goats are most common during the fourth month of pregnancy (9). Men’s clinical manifestations of the disease include weakness, fever, excessive sweating, especially at night, weight loss, and generalized body aches (10). Swelling in the testes and burning micturition caused by orchitis and urethritis, respectively, are unusual symptoms of the disease in men (5, 11). The disease has also been reported in wild and marine mammals, as well as birds, in recent years. Another epidemiological concern is the presence of brucellosis in wild animals, with the potential for continuous transmission to domestic animals and from them to humans (12).

Prevalence studies for brucellosis have been carried out in various parts of the country. Brucellosis in animals and humans has been reported in various parts of Ethiopia, most notably in cattle in both intensive and extensive management systems (13–17). The disease has also been reported among small ruminants in pastoral areas of the country. In a study conducted in the Tallalak district of the Afar region, a prevalence of 13.7% in sheep and goats was reported, with the prevalence being higher in goats (15.4%) than in sheep (10.6%), as reported by Wedajo et al. (18), whereas in the Somali region, Mohammed et al. (19) reported a seroprevalence of 1.37% among small ruminants in three woredas of the Jigjiga zone.

Unpasteurized milk products, infected placental material, aborted fetuses, or infected animals, which can shed a variety of bacteria after abortion, are other ways in which this infection in humans can occur in endemic countries (20). Pastoralist communities are more likely to contract brucellosis and other zoonotic diseases than other communities that do not have the same level of association with animals due to their close physical proximity to livestock and their reliance on animal products (19, 21).

The prevalence of brucellosis in pastoralist areas is thought to be influenced by several variables, including grazing patterns, management techniques, and the age and sex composition of herds (22, 23). Additionally, for a variety of reasons, pastoralists do not isolate or get rid of animals that may be infected with Brucellosis, which raises the risk of transmission to healthy animals. Female sheep and goats are kept in the herds for a longer period than males and are sold as soon as they mature. Unlike males, infected females shed the bacteria more frequently and may contribute to the likelihood of brucellosis in pastoral areas. Other factors contribute to the prevalence of brucellosis in pastoralist areas, such as the consumption of unpasteurized milk; unsafe handling and improper disposal of potentially infective materials, such as aborted fetuses, fetal membranes, and bodily fluids, which may contain concentrations of the bacteria; and a lack of awareness about zoonotic risks and methods of transmission (4, 16, 17, 20).

Nonetheless, the extent of the disease and its impact on pastoralist health are understudied, at least in the context of the proposed study area: the Korahey zone. Similarly, no research has been done on the risk factors associated with disease occurrence or the existing knowledge, attitudes, and practices in pastoralist areas that may play a role in zoonotic transmission. Therefore, the objective of this study was to estimate seroprevalence and associated risk factors of brucellosis in small ruminants in selected districts of the Korahey zone, Somali regional state, Ethiopia.

In this study, the animal-based seroprevalence of small ruminant brucellosis in three districts of the Korahey zone of Somali regional state was 1.23% and this was in line with the results reported by Mohammed et al. (19) in the Jigjiga zone of the Somali region, with a prevalence of 1.37%; Tsegay et al. (28) in Debrezeit and Modjo, with a seroprevalence of 1.76%; and Dabassa et al. (29), who found a similar result (1.56%) in a study of small ruminant brucellosis in Yabello. The present finding is lower than results reported by Aloto et al., (30) who reported 4.1% in two zones of southern Ethiopia, Dosa et al. (31) who reported 3.33% in two selected districts of Wolaita Zone southern region, Teshome et al. (32) who reported 17.36% in goats in Borana pastoral area, Deddefo et al. (33) who reported 4.6% in Arsi, Teshale et al. (34) who reported 9.7% in Afar, and Negash et al. (35) who reported 9.11% in the Dire Dawa area. Similarly, Wedajo et al. (18) reported a higher seroprevalence (13.7%) in the Tallalak district of the Afar region.

However, the current result is relatively higher than the previous study by Ferede et al. (36) who reported 0.4% in and around Bahirdar and Tewodros and Dawit (37) who reported 0.7% in and around Kombolcha, Amhara region. This variation might be caused by variations in sample size, agroecological location, and animal management practices.

In the present study, RBPT was used to detect the seroprevalence of Brucella species in small ruminants which was used in this study to screen individual animals, is a low-cost, quick, and highly sensitive test (27). However, due to cross-reactivity with antibodies from closely related gram-negative bacteria such as Yersinia enterocolitica, Escherichia coli, Salmonella spp., and Sternotrophomonas maltophilia as well as antibodies produced by the B. abortus S19 vaccine, its specificity is low (38). In the current study, only samples that gave signals for both RBPT and CFT were considered positive since no single test is appropriate in all epidemiological situations due to problems of sensitivity and or specificity of the tests as recommended by OIE (27) and other reports (39).

The current study revealed that the seroprevalence of brucellosis was 1.57 times higher than sheep’s seroprevalence, although this difference was not statistically significant. This finding is comparable to that of Mohammed et al. (19), who also reported higher seroprevalence in goats in the Somali region. Similar findings were also reported by Wedajo et al. (18), Teshale et al. (34), and Ashenafi et al. (40) in the Afar region; Aloto et al. (30) in two zones of southern, Ethiopia; Mengistu (41) in Konso, southern Ethiopia; Tewodros and Dawit (37) in Kombolcha of the Amhara region; and Negash et al. (35) in Dire Dawa.

However, a study by Bekele and Kasali (42) in the central highlands of Ethiopia and Samaha et al. (43) in Egypt showed a higher prevalence in sheep than in goats, mainly due to differences in husbandry systems and the susceptibility of the sheep and goat breeds in the particular area. The difference may also be due to variations in the species breakdown of the samples examined by the various researchers. Because goats are more susceptible to Brucella infection than sheep and excrete the bacterium for a longer period of time, goats exhibit higher seroprevalence than sheep (21).

The seroprevalence of brucellosis of female sheep and goats were higher than males one, although this difference was not statistically significant (p > 0.05). The result of this study is in agreement with other findings by Tewodros and Dawit (37) and Yesuf et al. (44), who also reported higher seroprevalence in females than in males, although Yesuf et al. (44) found a statistically significant (p < 0.05) difference in Brucella seroprevalence between the two sexes. The lower number of males (n = 48) sampled and tested compared to a higher number of females (n = 276) in the sample may have contributed to the higher female animal seropositivity. It is also possible that male animals are less likely to contract Brucella infection because they do not contain erythritol (45). The fact that there was no statistically significant difference between the two sexes may also have contributed to the very low number of positive results observed in the current study.

The study revealed a significantly (p < 0.05) higher seroprevalence of small ruminant brucellosis in the old age group than in the medium and young age groups. This is consistent with the findings of Tsegaye et al. (28) and Adugna et al. (46), who also reported a higher seroprevalence of brucellosis in small ruminants more than 2 years of age than in the younger age categories. Similarly, Megersa et al. (14), Mohammed et al. (19), and Tigist et al. (47) reported higher seroprevalence in older age groups than in younger animals, even though the difference was not statistically significant. In contrast, Wedajo et al. (18) and Negash et al. (35) reported a higher seroprevalence in younger animals than in adult sheep and goats.

The study also found a statistically significant association between seroprevalence and parity stage, with higher seropositivity in higher parity stage females than in lower parity stage females. The various findings regarding the variation in brucellosis seroprevalence among the various age groups may be related to variations in the relative proportion of the various age groups in the samples examined by the various researchers. The risk of contracting Brucella infection is higher in sexually mature and pregnant animals than in sexually immature animals of either sex. This might be due to the concentration of erythritol and sex hormones, which promote the growth and reproduction of Brucella species organisms, rising with age and sexual maturity (48).

In the present study, the relationship between Brucella seropositivity and the presence of reproductive issues, such as a history of abortion or retained fetal membranes, was investigated. Male animals of both species were excluded from this discussion because no male animals tested positive for Brucella infection by chance. The seroprevalence of brucellosis in small ruminants with a history of abortion or retained fetal membranes was found to be higher (p < 0.05) than in those without these problems. Similar findings were reported by Wedajo et al. (18) and Wubishet et al. (49) in the Afar and Guji zones of the Oromia region, respectively. It is known that abortion in livestock represents the major complaint attributed to Brucella infections (50–52).

The seroprevalence of brucellosis was higher in large (>60 heads) herds’ sizes than in small (≤60 heads), but the difference was not significant. This is in line with the findings reported by Wedajo et al. (18) in the Afar region. Walker (53) shows that herd sizes and animal densities are directly related to disease prevalence and complicate infection control in a population. Similarly, sheep and goat herds kept alongside other livestock species had higher brucellosis seroprevalence than herds kept solely, where the owner did not own any other livestock species besides sheep and goats.

The introduction of new animals from unscreened herds into sheep and goat herds was a major risk factor observed in this study. Pastoralists usually introduce these animals into the herds as replacement stock through purchases, gifts, or donations from relatives. This finding is consistent with the findings of several authors who discovered that the introduction of animals from non-free Brucellosis herds or herds with unknown Brucellosis status was a major factor associated with Brucellosis in sheep, goat, and cattle herds (50, 54–57).

Other research suggests that introducing infected animals can increase individual-level prevalence because the longer they are in contact with the rest of the herds, the greater the risk of spread (1, 58). Animal movement between herds has also been found to be a potentially dangerous practice. One suggested key preventive measure is to avoid the introduction of infected animals by maintaining completely closed herds or by carefully screening purchased animals before introducing them into the herds, a practice that is very uncommon in pastoral communities. There is evidence that one of the main causes of most brucellosis control campaigns’ ineffectiveness is the lack of control over the movement of animals, and this suggestion is supported by available data (12, 50, 56).

Seroprevalence was higher in herds with female animals that had abortions in the previous year compared to herds without abortions, but this difference was not statistically significant. Tigist et al. (47) and Obonyo (59) revealed a statistically significant correlation between a herd’s seropositivity to Brucella and the presence of female animals that had recently given birth. Brucellosis causes late-term abortions, which increases the risk of the disease spreading to other animals in the herds while they graze on the contaminated pasture lands because aborting animals typically shed the bacteria into the environment. Abortion represents the major complaint attributed to Brucella infections in livestock (4, 50–52, 60). It is known that females infected with brucellosis shed considerable amounts of the pathogen in milk, placental membranes, and aborted fetuses. Such females have been reported to shed organisms for several months (4, 48, 60). This causes environmental contamination, which increases the risk of pathogen transmission between animals in the same herds as well as other herds during free mixing in grazing and watering areas.

Lending or sharing male animals with other herds for natural breeding purposes was significantly associated with herd seropositivity. Other authors have reported that lending male animals for breeding is a risk factor for Brucella seropositivity in animals (59, 61). Although the venereal route is not regarded as a key channel for Brucella transmission in small ruminants under natural settings, procedures that entail the movement of animals between herds s are deemed problematic because of the possibility of mechanical transmission (5, 12, 48).

Although not significant, seropositivity was higher in herds that came into contact with other herds in the past year. This could be attributed to the pastoral lifestyle, which is characterized by the frequent mobility of herds. Considering the contagious nature of Brucella spp. sharing shared grazing areas and drinking holes makes it easier for possibly infected cows and clean herds to spread infections such as brucellosis and others (14, 62).

The current study was limited to the seroprevalence of the small ruminant brucellosis only and did not include other such as cattle and camels are susceptible to brucellosis and both species are kept in the study area but they were not part of the current study. The study also did not attempt to assess the prevalence level of the disease in humans to correlate findings in the animals. The present study did not attempt culture of Brucella species and therefore was not able to identify the various species and biovars of Brucella species circulating in sheep and goats in the study area.

The present study revealed that the seroprevalence of brucellosis in sheep and goats was found to be relatively low at both the individual animal and the herd level. However, the multivariable logistic regression analysis revealed that none of the proposed risk factors were not significantly associated with Brucella seropositivity at individual and herd level. In conclusion, awareness campaign among pastoral community of the seriousness of the causes, modes of transmission, symptoms, risk factors, and methods of prevention of the disease should be undertaken as soon as possible. For effective control of brucellosis that may be present in the area, an integrated approach should be promoted that takes into account the relationship between humans, animals, and the environment in the context of “One Health approach.”

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

The animal studies were approved by the Jigjiga University, College of Veterinary Medicine-Research Review Committee (Protocol No. JJU/CVM/clis/022/14). The studies were conducted in accordance with the local legislation and institutional requirements. Written informed consent was obtained from the owners for the participation of their animals in this study.

AMH, FA, AHH, AM, and HG contributed to data collection, study design, and interpretation, manuscript draft, and writing. AMH, FA, and AHH contributed to the conception of the research idea, study design, data analysis, writing, revising and editing, the design of the study, and data interpretation. AM and HG contributed to the reference search and manuscript writing and editing. All authors approved the submission of the final manuscript.

This study was funded by the Jigjiga University Research and Community Service Vice President Office.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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