Chemokine, cytokine and haematological profiles in Sprague-Dawley rats co-infected with Plasmodium berghei ANKA and Trichinella zimbabwensis-A laboratory animal model for malaria and tissue-dwelling nematodes co-infection.

Malaria remains a major cause of mortality and morbidity in sub-Saharan Africa (SSA) and tissue-dwelling helminth parasites (TDHPs) are also prevalent in this region presenting a geographical overlap in endemicity. There is paucity of information on the specific host immune responses elicited at different phases of the life cycle by the co-infecting helminth parasites. This study aimed at using a laboratory animal model to determine selected chemokine, cytokine and hematological profiles in Sprague-Dawley rats co-infected with Plasmodium berghei ANKA (Pb) and a tissue-dwelling nematode, Trichinella zimbabwensis (Tz). One-hundred-and-sixty-eight male Sprague-Dawley rats (90-150g) were randomly divided into four experimental groups; Control (n = 42), Pb-infected (n = 42), Tz-infected (n = 42) and Pb + Tz-infected group (n = 42). Trichinella zimbabwensis infection (3 muscle larvae/g body weight per os) was done on day 0 while intra-peritoneal Pb infection (105 parasitised RBCs) was done at day 28 of the 42-day experimental study for the co-infection group which corresponded with day 0 of the Pb group on the protocol. Haematological parameters, cytokines (TNF-α, IL-10, IL-4, IL-6), chemokines (CXCL10, CCL5, CCL11) and burden of Tz adult worms and muscle larvae burden were determined as per need for each group. Results showed that Tz infection predisposed the co-infected animals towards rapid development of Pb parasitaemia during co-infection, reaching a higher peak percentage parasitaemia at day 7 post-infection than the Pb mono-infected group at day 6 post-infection. Animals in the co-infected group also exhibited severe anaemia, basophilia, neutrophilia, eosinophilia and lymphopenia at day 7 post Pb infection compared to the control groups. Significant elevation of Pb parasitaemia coincided with elevated pro-inflammatory cytokine TNF-α (P < 0.001), regulatory anti-inflammatory IL-10 (P < 0.001), and pro-inflammatory chemokines CXCL10 (P < 0.001) concentration in comparison to control group, at day 7 post Pb infection. Our results confirm that co-infection of Pb with Tz resulted in increased Pb parasitaemia compared to the control group in the early stages of infection and this might translate to severe malaria.