Date Published: December , 2017
Publisher: Makerere Medical School
Author(s): Aquino Qouilazoni Ukuli, Kizito Kahoza Mugimba.
Hepatitis E (HE) caused by Hepatitis E virus (HEV) is an emerging global public health threat. It has been identified as potentially zoonotic and swine act as main reservoirs.
The objective of this study was to determine the seroprevalence and risk factors associated with HEV in swine abattoir workers.
This was a cross-sectional study where 45 workers were sampled (N=50), serum collected and tested for presence of anti HEV IgM using ELISA.
A seroprevalence of 13.3% was obtained with the highest 50% among slaughterers and the lowest amongst sanitary cleaner, cloth cleaners and inspector. Those in direct contact with live pigs, their carcasses and tissues were at a higher risk compared to those in indirect contact. Seroprevalence was seen to increase with age, with the highest rate among those above 24 years.
There is silent HE virus infection in abattoir workers at Wambizi as reflected by presence anti HEV IgM in 13% of the tested serum. However, no single case of HE has ever been reported in swine abattoir workers or general population in Kampala city. This silent maintenance of HEV infection amongst swine abattoir workers is an occupational risk that could challenge public health systems.
A cross-sectional study was carried out in Wambizi pig abattoir located in Nalukolongo, Lubaga Division, in Kampala, Central Uganda. The abattoir supplies pork to consumers in and around Kampala. The study population involved abattoir workers at the different levels of the pork value chain within and around the abattoir. Although sampling was intended for all the 50 workers, only forty five workers were present at the day of sampling. Blood (2mls) was collected from 45 abattoir workers (90%) by venous puncture into plain vacutainer tubes labeled with the subjects’ unique identification number. Quantitative data was collected using a structured questionnaire to assess the risk factors for transmission of HEV. This Sampling was conducted in April 2015. Ethical clearance to conduct this study was obtained from Makerere University, School of Medicine’s research and ethics committee. Informed consent was sought from the participants before sampling.
Six out of forty five samples collected tested positive for anti HEV IgM, giving a general seroprevalence of 13.3% at a confidence interval of 95%. Specifically seroprevalence varied with the activity someone was involved in (identified as risk factors) as summarised in table 1.
The results showed 50% (3/6) of the positive samples were from study subjects directly involved in the slaughter of animals (slaughterers), 16.67% (1/6) for the traders, suppliers and cooks.
This study was done in a population of swine abattoir workers where HE infection has not been reported either in workers or in pigs. A seroprevalence of 13.3% (n=45) was observed. The general seroprevalence range reported in developing countries is 3–80%41–42. Studies in healthy individuals in the United States where HEV is not endemic indicated a significant proportion of anti HEV antibodies of up to 22%43–44. This increased seroprevalence in a developed country is associated with consumption of swine products such as pork and pig liver and travelling to areas where HEV is endemic. Other studies done in Africa indicated a seroprevalence ranging from 6–80%41. In Egypt a country where pork consumption is uncommon due to the dominant Islamic religion, HEV seroprevalence was reported to be 80%41. This can be attributed to other routes of transmission r than pork consumption probably the oral faecal route or other zoonotic sources. Hepatitis E virus RNA has been detected in faecal wastes and has been seen to persist in the environment45–46. In developing countries where farming methods and sewage treatment are poor, introduction of faecal wastes in the water system is likely. This compromises water quality and increases chances of disease outbreak. Exposure to animal wastes and fluids is another important source of infection47.
There is silent HEV infection amongst abattoir workers at Wambizi, as reflected by the high seroprevalence and this should raise public health concern. This silent infection is maintained by other means than pork consumption. Direct contact with pigs and pig products has high association with HEV infection. More investigation involving pigs and more humans in various occupations should be conducted to help understand the epidemiology of HEV and guide control measures. Bearing in mind that recent HE outbreaks in Uganda have been sporadic with an elusive primary source, such studies would improve our understanding of HEV epidemiology.