Background: Malaria and intestinal coccidian parasites are both protozoan and their interaction in co-infected patients is still not clear. Patients infected with both malaria and coccidian parasites experience diarrhoea, gastro-intestinal and health problems that maybe life threating. We studied opportunistic intestinal coccidian parasites (OIPs) and the human immunodeficiency virus (HIV) in adult patients with malaria in Fundong Health District, Northwest of Cameroon. The objectives was to determine prevalence, and distribution of the diseases in adult population. 
 Methods: A prospective cross-sectional study carried out between April and December 2022. Malaria patients were identified by the presence of the Plasmodium parasite in Giemsa blood-stained films. HIV status was determined using the rapid diagnostic test (RDT). Stool samples were subjected to wet preparation and formol-ether concentration technique to detect intestinal coccidian parasites. Pearson’s Chi-Square (χ2) and binary logistic regression were performed as part of the statistical analysis. Statistical significance was set a P-value<0.05.
 Results: Three hundred and thirty (330) adult patients all infected with malaria took part in the study, 115(35%) males and 215 females (65%). The adult were of age 21 years and above. The mean age of participant was 37.02(±15.235) years. Malaria co-infection with coccidian parasites was observed in 19.4%. Malaria co-infection with other gastro-intestinal intestinal parasite capable causing pathological conditions in patients was 5.5%. The study showed the prevalence of malaria co-infections with HIV was 8.2%. The mixed infections observed were domestically acquired (57.8%) as well as travel related (46.2%). Fever was most reported in severe malaria 315/330 (95%), followed by those who reported abdominal pains 85/330 (26%), while diarrhoea was reported in 35/330 (11%) of the study participants. Fever, and abdominal pain significantly associated with malaria status (simple or severe malaria) p-value=, P-value= respectively (5.915) 0.015, P-value= (8.3) 0.004, as well as the HIV status P-value= (11.798) 0.003. The odds of developing severe malaria from fever was 3.533(CI: 1.204-10.366) times higher compared to those who did not have fever. The odds of developing severe malaria from abdominal pain was 0.420(CI: 0.230-0.767) less. Results showed living with child<2 years, water treatment methods, material use in hand washing, predicted the probability of coccidian infection in the final logistic regression model accounting for 23.6% of the variance in the coccidian infections was explained by the model.
 Conclusion: Prevalence of malaria, and opportunistic intestinal coccidian infections in adult patients was significantly influenced by migration, seasonal variation and the individual’s immune status. Routine clinical practice have often ignore the investigation of possible mixed infections especially in persons with compromised immunity including HIV. Screening patients suspected of malaria should include investigation for opportunistic intestinal coccidian parasites especially for HIV and other vulnerable populations. An integrated prevention and control strategy need to be considered.