Brucellosis and bTB are zoonotic diseases that are endemic in Rwanda. This study aimed to investigate, for the first time in Rwanda, the awareness of the transmission of zoonotic diseases (brucellosis, bTB, cysticercosis, leptospirosis, and Q-fever), the history of diseases among 118 abattoir workers during the three years before this survey, occupational hazards associated with daily practices and behaviors of workers, and to assess the association between exposure and outcome variables. This study found that abattoir workers (82.2%) were more aware of the transmission of zoonotic tuberculosis than brucellosis (27.1%). Few workers have heard of cysticercosis (12.7%), leptospirosis (10.2%), and Q-fever (8.5%) weather in animals or humans. Practices and behaviors predisposing abattoir workers to zoonotic diseases were recorded in this study. There was a significant association between the awareness of zoonotic diseases (TB and brucellosis) and the occupation (p = 0.05 and p < 0.001), as well as the level of education (p < 0.001) of abattoir workers.
The level of awareness was higher for the transmission of zoonotic TB than brucellosis and other diseases. The high awareness for zoonotic tuberculosis transmission may be due to the regular occurrence of tuberculous lesions in slaughtered cattle resulting in the condemnation of the carcasses (one case occurred during this study), and abattoir workers being aware of colleagues, friends, and relatives with tuberculosis infection as mentioned by respondents during this study. Moreover, abattoir workers are required to present an annual certificate of medical examination which could have raised awareness of tuberculosis. Moreover, one cleaner had recovered from tuberculosis in the past and during this study, two abattoir workers were diagnosed with TB and placed into isolation but we could not trace the origin of the infection for all these cases due to the inability of laboratory tests to distinguish MTBC species (14, 16). Furthermore, extra-pulmonary human cases due to M. bovis (38, 39) may be missed because lymph nodes biopsies are rarely collected for the diagnosis of human TB. Instead, sputum is the specimen of choice to be tested (39). The level of awareness for zoonotic tuberculosis transmission found in this study was consistent with 93.3% that was reported in central Ethiopia among abattoirs workers (40). Therefore, the awareness of zoonotic TB may be commonly high among abattoir workers.
The low awareness for zoonotic brucellosis transmission was consistent with a recent study on brucellosis in women presenting with abortions in Nyagatare district hospital, Rwanda (5). This low awareness may be attributable to the lack of routine diagnosis and treatment of human brucellosis in hospitals and health centers in Rwanda. Human brucellosis may therefore be misdiagnosed for other acute febrile diseases namely typhoid fever and malaria (25). Moreover, the level of awareness for zoonotic brucellosis transmission (27.1%) obtained in this study was lower than that (44.2%) reported in Ethiopia (41) and (76%) Tanzania (42) among abattoir workers. These differences may be due to the lower level of education of abattoir employees in Rwanda. The seroprevalence of brucellosis ranges from 6.1–25.0% in women presenting abortions in Rwanda (5, 7). Therefore, the low awareness observed in the present abattoir study may simply imply that the brucellosis prevalence may be higher in occupational groups who come frequently in contact with animals. There is thus a need for interdisciplinary collaboration, raising the awareness and knowledge of human health professionals and including human brucellosis among the routinely diagnosed and treated diseases in Rwanda.
The low awareness for cysticercosis (12.7%) and leptospirosis (10.2%) recorded in this study was lower than the 89.0% and 33.0% recorded in Kenya for cysticercosis and leptospirosis, respectively (43). This indicates that abattoir workers from Rwanda were probably less trained on these diseases compared to their neighbors thereby the need to enhance education in Rwanda. Furthermore, a 3.0% prevalence of bovine cysticercosis was reported at Nyagatare district slaughterhouse, Rwanda (35), and a high prevalence of 21.8% of cysticercosis was reported in people with epilepsy in the Southern Province of Rwanda (36). These findings show that leptospirosis, Q-fever, and cysticercosis may be endemic in Rwandan cattle and thus constitute a risk of infection for workers in abattoirs with poor hygienic and biosafety measures.
The majority (67.8%) of abattoir workers reported that they had been sick within the three years before the survey and 7.6% confirmed contracting diseases from the abattoirs. Apart from malaria that was reported by 48.3% of workers, other workers could not remember names of diseases diagnosed in the last three years, instead, they reported the symptoms. Diarrhea was a symptom of unknown origin which was reported by seven participants (28.0%) of which five reported eating while working. This was not surprising since cases of diarrhea are commonly reported among abattoir workers (44-47). Other symptoms that were reported included fatigue (11.0%) and flu (9.3%) that were reported by malaria-negative patients, and fever (15.3%), headache (5.1%), abortion (0.9%), orchitis (0.9%), as well as nephritis-related symptoms (3.4%) of unknown origin. However, these symptoms are commonly observed in humans with diseases like brucellosis (48), leptospirosis (49), and Q-fever (50) as earlier reported among abattoir workers (22, 51). Alghought, these diseases have never been reported in abattoir workers in Rwanda, brucellosis seroprevalence has been reported in 10.0% of workers in neighboring Uganda (52), and 19.5% in Tanzania (22), and odds of contracting brucellosis were higher among abattoir workers compare to other occupational groups in Uganda (53). The nephritis-related symptoms may also be caused by M. bovis which has been isolated in the urogenital tract of humans (54). Abattoir workers being regularly exposed to carcasses, blood, urine, and hides from infectious animals are at high risk of contracting these diseases. There is therefore a need to investigate and control various diseases in animals to protect abattoir workers and consumers. It is also necessary to educate workers on zoonotic diseases and hygienic practices and provide them with appropriate personal protective equipment (PPE).
Practices and behaviors predisposing abattoir workers to zoonotic diseases were recorded in this study. Most (70.3%) of workers cut their hands while only meat inspectors wore gloves (9.3%), and 39.8% of employees worked with bare and injured hands. The frequency of hand-cut injuries in this study was higher than the 47.0% reported in Nigeria (55), and the proportion of wearing gloves was lower than 18.6% reported in Ethiopia (41). This is of concern since working with bare and injured hands had been associated with the risk of contracting brucellosis in Nigeria (21). Moreover, certain workers of this study (28.0%) had their breakfast while working, and this proportion of workers was higher than 14.4% reported in Nigeria (55). In this study, the majority (74.6%) of workers experienced splashes of fluid or blood onto their faces (eyes, nostrils, and mouth) while none wore facemasks and goggles. This is worrying because a study in Tanzania demonstrated that abattoir workers that did not adhere to the hygiene and use of protective gears were three times more at risk of contracting brucellosis (52). The practices of working with bare and injured hands, and eating while working, as recorded in this study confirm the low awareness and poor epidemiological knowledge of pathogens causing zoonotic diseases. There is therefore a need for the concerned veterinary public health authorities to strengthen the implementation of rules and regulations regarding the biosafety in abattoirs and raise awareness of the abattoir workers and other stakeholders, through educational campaigns.
Univariate and correspondence analyses showed that there was a significant association between the awareness for zoonotic TB and brucellosis and the occupation (p = 0.05, p < 0.001), as well as the level of education (p < 0.001). This was in agreement with studies in Nigeria (21), Tanzania (42), and Ethiopia (41). In this present study, meat inspectors and workers with secondary education were more likely to be aware of zoonotic tuberculosis and brucellosis than other occupational and educational group categories. Moreover, our findings showed that 54.5% of workers with secondary education were meat inspectors, and most of them had a veterinary education background while others had gained knowledge and skills through work experience which can explain the higher level of awareness. Therefore, education should raise the awareness among other workers.
Both univariate and correspondence analyses showed that being sick within the three years before the study was significantly associated with an occupation (p = 0.003), the level of education (p = 0.003), and the duration at work (p < 0.001). Transporters of carcasses and butchers, workers with primary education, and workers with experience of three years and above were more likely to become sick than other group categories. This is in agreement with the findings in Nigeria in which illiterate and workers with primary education were more likely to become seropositive to brucellosis (21, 41). Generally, workers with lower levels of education are assigned to cleaning and washing viscera, jobs in which workers lack the understanding of the high burden of harmful microorganisms they are exposed to. Abattoirs workers with more than five years at work were more likely to be seropositive to Brucella spp. in Nigeria (21), while those with more than 40 years at work were more likely to be positive to M. bovis (56). This affirms the association between age and illnesses, in that, workers with advanced age and weakened immune systems may have been exposed to the pathogens for a long period, leading to a greater risk of contracting infections. Slaughtered cattle are the sentinels of zoonotic and other animal diseases. Thus, if meat inspection findings can be confirmed by laboratory evidence, this would play a significant role in the surveillance and control of infectious diseases.