SKIN AND SERUM REACTIVITY AMONG HUMANS TO HISTOPLASMIN IN THE VICINITY OF A NATURAL FOCUS OF HISTOPLASMA-CAPSULATUM VAR DUBOISII

The epidemiology of histoplasmosis duboisii (African histoplasmosis) i s not well understood. The present study was carried out to investigat e the prevalence of skin sensitivity and to determine by immunodiffusi on the presence of antibodies among humans to histoplasmin around a re cently discovered natural focus of Histoplasma capsulatum var. duboisi i in a bat cave in Ogbunike in the Anambra State of Nigeria. Out of th e 40 subjects, all young adults aged 18-30 years, comprising cave guid es, traders and farmers examined in the immediate vicinity of the cave , 14 (35.0%) gave a positive skin test. In another population of the s ame age group, comprising 620 persons, viz. traders, farmers, palm oil workers and some patients attending rural clinics, examined in other nearby areas in Anambra State, 55 (8.8%) reacted positively to histopl asmin. In the immunodiffusion tests, 2 (2.08%) of the 96 school childr en and 17 (9.4%) of the 181 young adults, including farmers, palm oil workers and traders tested amongst the population around the cave, dem onstrated precipitating antibodies to histoplasmin in their sera. Only 5 (0.79%) of the 630 adults of the same age group with similar occupa tions examined from other areas in Anambra State had precipitating ant ibodies. Out of another 50 subjects examined, viz.; wood workers, trad ers, farmers, and school teachers in Nsukka in the Enugu State, two (4 .0%) demonstrated antibodies. It is suggested that asymptomatic infect ions due to the duboisii variety of H. capsulatum may be common in the human population around the cave. A diligent search with the help of local hospitals and public health officials may reveal clinical cases of histoplasmosis duboisii with cutaneous and systemic lesions.