Antigenic cross reaction between malaria parasites and typhoid organisms in patients with fever of unknown origin in Owerri

This study reports result of malaria parasite test, Widal test and bacteriological test was carried out on 205 samples. Of these, 160 were cases of patients presenting malaria-like symptoms while 45 were healthy controls. Out of the 160 patients studied, 117(73.1%) had acute malaria, while 18(40%) out of the 45 control sample were malaria parasite carriers. Widal test was done to determine those positive for anti-salmonella antibodies, Widal titers ≥ 1/160 which is considered very specific for diagnosis of typhoid fever. This test was positive for salmonella 'O' and 'H' titers in 57(48.7%) and 3(16.7%) of malaria patients and carriers respectively. Statistical analysis showed that there is a relationship between malaria parasite load and the level of salmonella antibody titres. Bacteriological test was then carried out to determine the isolation rate of S. typhi. Only 3(2.6%) of the malaria patient samples were positive for typhoid by the blood culture method. There were no isolation in the carrier group. On four weeks follow up, after malaria treatment, 38 of the 54 samples showing widal positive without S. typhi isolate were retested and 29(76.3%) become negative. It was postulated that the stimulation of the immune system due to acute malaria infection could be responsible for this phenomenon. The rate of co-infection with malaria parasites and S. typhi was high when typhoid was diagnosed by widal (29.3%) than by blood culture method(1.50%). The incidence of typhoid and malaria co-infection will greatly reduce if the diagnosis of typhoid fever in malaria endmic areas as Owerri is based on blood culture. Keyword: Antigenic cross reaction, malaria parasite and S.typhi in patients INTRODUCTION uman malaria, caused by four protozoan parasites of the genus Plasmodium, is a disease responsible for inordinate mortality, morbidity, and economic loss worldwide. Malaria infects up to 500 million people per year and is responsible for almost 3 million deaths annually (Snow et al., 2005). Plasmodium parasites responsible for *Corresponding author: [email protected] Ajero,C.M.U1 Copyright © 2015 Nigerian Society for Microbiology human malaria are obligately dependent on mosquitoes of the genus Anopheles for transmission from one human host to the next, with Anopheles gambiae being the primary vector in Africa (Fontenille and Simard 2004). Typhoid fever, or commonly just typhoid, is a common worldwide illness, is caused by Salmonella typhi and transmitted by the ingestion of food or water contaminated with the faeces of an infected person (Giannella 1996). The H Nigerian Journal of Microbiology 2015, 28: 2892-2901 Published online at www.nsmjournal.org