Effect of Co-Infection with Intestinal Parasites on COVID-19 Severity: A Prospective Observational Cohort Study (preprint)

ABSTRACT

Background: COVID-19 symptomatology in Africa appears significantly less serious than in the industrialized world. We and others previously postulated a partial explanation for this phenomenon, being a different, more activated immune system due to parasite infections. We investigated this hypothesis in an endemic area in Africa. Methods: Ethiopian COVID-19 patients were enrolled and screened for intestinal parasites. The primary outcome was the proportion of patients with severe COVID-19. Logistic regression models were used to estimate the association between parasite infection, and COVID-19 severity. Models were adjusted for sex, age, residence, and comorbidities. Findings: 751 SARS-CoV-2 infected patients were enrolled, of whom 284 (37·8%) had intestinal parasitic infection. Only 27/255 (10·6%) severe COVID-19 patients were co-infected with intestinal parasites, while 257/496 (51·8%) non-severe COVID-19 patients appeared parasite positive (p<0.0001). Patients co-infected with parasites had lower odds of developing severe COVID-19, with an adjusted odds ratio (aOR) of 0·14 (95% CI 0·09–0·24; p<0·0001) for all parasites, aOR 0·20 ([95% CI 0·11–0·38]; p<0·0001) for protozoa, and aOR 0·13 ([95% CI 0·07–0·26]; p<0·0001) for helminths. When stratified by species, co-infection with Entamoeba spp. , Hymenolopis nana, and Schistosoma mansoni implied lower probability of developing severe COVID-19. There were 11 deaths (1·5%), and all were among patients without parasites (p=0·009). Interpretation: Parasite co-infection is associated with a reduced risk of severe COVID-19 in African patients. Parasite-driven immunomodulatory responses may mute hyper-inflammation associated with severe COVID-19. Funding: European and Developing Countries Clinical Trials Partnership (EDCTP) and Joep-Lange Institute.Declaration of Interests We declare no competing interests.Ethics Approval Statement The study protocol was reviewed and approved by the Health Research Ethics Review Committee of Mekelle University College of Health Sciences (No. ERC 1769/2020), the Ethiopian Public Health Institute (No EPHI 6.13/814), and Eka Kotebe General Hospital (No. EK/150/5/32). Written informed consent was obtained by all participants, or their guardians, for participation in the study.