Parasite density and serum cytokine levels in Plasmodium vivax malaria in Turkey

SUMMARY We aimed to investigate the relationship between quantitative Plasmodium vivax parasitaemia and serum cytokine levels in a highly endemic region of Turkey, where such a relation has not been investigated before. Active screening was done in a total of 1316 people residing in 33 villages of Sanliurfa province, Turkey. The study population consisted of 79 consecutive patients with P. vivax malaria, and a control group included 89 healthy subjects. Thick blood smears were examined for malaria parasite and parasite count. Serum samples were analysed for IL‐1β, IL‐2, IL‐4, IL‐6, IL‐8, IL‐10 and IL‐12 by the ELISA method. Compared to controls, levels of pro‐inflammatory cytokines, i.e. IL‐1β, IL‐6 and IL‐12, were significantly higher in patients with parasitaemia. There was a significant positive correlation between serum IL‐10 and IL‐12 levels and the parasite burden ( r = 0·264, P = 0·024 and r = 0·264, P = 0·024, respectively). Serum IL‐8 levels showed a significant negative correlation with parasite burden ( r =– 0·356, P = 0·002). There was a positive correlation between IL‐8 levels and age, while the opposite was observed for IL‐12. High fever was correlated with IL‐6 and IL‐10 levels. Compared to controls, patients with a parasite count greater than 5000/µL had a significantly higher IL‐1β and IL‐10 levels ( P < 0·05), while the difference was not significant for patients with a parasite count less than 1000/µL. Thus, we can conclude that pro‐inflammatory response against P. vivax gains more importance during periods of increased parasite burden.