First Report of the Occurrence of Trichinella-Specific Antibodies in Domestic Pigs in Central and Eastern Uganda

Abstract

Previous research on trichinellosis in Africa focused on isolating Trichinella from wildlife while the role of domestic pigs has remained highly under-researched. Pig keeping in Uganda is historically recent, and evidence on zoonotic pig diseases, including infection with Trichinella species, is scarce. A cross-sectional survey on Trichinella seroprevalence in pigs was conducted in three districts in Central and Eastern Uganda from April 2013 to January 2015. Serum from a random sample of 1125 pigs from 22 villages in Eastern and Central Uganda was examined to detect immunoglobulin G (IgG) against any Trichinella spp. using a commercially available ELISA based on excretory-secretory antigen. ELISA positive samples were confirmed using Western Blot based on somatic antigen of Trichinella spiralis as recommended in previous validation studies. Diaphragm pillar muscle samples (at least 5 g each) of 499 pigs from areas with high ELISA positivity were examined using the artificial digestion method. Overall, 78 of all 1125 animals (6.9%, 95% CI: 5.6–8.6%) tested positive for antibodies against Trichinella spp. in the ELISA at significantly higher levels in Kamuli district compared to Masaka and Mukono districts. Thirty-one percent of the ELISA positive samples were confirmed IgG positive by the Western Blot leading to an overall seroprevalence of 2.1% (95% CI: 1.4–3.2%). The large proportion of ELISA positive samples that could not be confirmed using Western blot may be the result of cross-reactivity with other gastrointestinal helminth infections or unknown host-specific immune response mechanisms in local pig breeds in Uganda. Attempts to isolate muscle larvae for species determination using the artificial digestion method were unsuccessful. Due to the large number of muscle samples examined we are confident that even if pigs are infected, the larval burden in pork is too low to pose a major risk to consumers of developing trichinellosis. This was the first large systematic field investigation of Trichinella infection in domestic pigs in Uganda and its results imply that further studies are needed to identify the Trichinella species involved, and to identify potential sources of infection for humans.

A preliminary survey of Trichinella spp. in pigs raised under controlled housing conditions in Colombia: 2014–2016

“…surveillance in pigs, according to the International Commission on Trichinellosis [ 7 ]. Since serology has been shown to occasionally yield false-positive results, or sometimes positive results with very low to undetectable levels of larval burden [ 4 , 23 ], it would be warranted that any seropositive pig be further confirmed by the artificial digestion assay. A study to evaluate the reproducibility and validation of an ELISA has shown that, when the recommended protocol is strictly followed, a negative result is an excellent indicator of the absence of infection, with a specificity of 98.29% [ 8 ].…”

Pigs' management practices and exposure to Trichinella spp. in pigs and warthogs in the northern area of Senegal

“…In the present study, the seroprevalence of Trichinella infection from pig muscle samples was 10.9% compared to 10.8% obtained in warthogs. Serological studies implemented in pigs in Egypt, Nigeria, and Uganda reported seroprevalence of 4.5%, 40%, and 6.9%, respectively [17][18][19]. This difference in prevalence observed could be due to the management mode of the different farms and the hygiene applied.…”

Using a Value Chain Approach to Map the Pig Production System in Rwanda, Its Governance, and Sanitary Risks

“…However, a high prevalence of porcine and human cysticercosis has been reported (44)(45)(46), as well as non-typhoidal Salmonella isolates which were recovered from pig faecal samples (47). In neighbouring countries, trichinellosis, salmonellosis, and cysticercosis have been documented in pigs (48)(49)(50)(51)(52) and in humans (53,54).With the exception of the single modern abattoir, slaughter houses had intercrossing of clean and dirty operations, from killing through to carcass preparation. This is likely to lead to cross-contamination with pathogens such as Salmonella (55), especially as no running water was available inside the visited slaughterhouses, as has been reported elsewhere (49).…”