Malaria in Brazilian military personnel deployed to Angola

Background: Malaria represents one of the most important infectious disease threats to deployed military forces; most personnel from developed countri es are nonimmune personnel and are at high risk of infection and clinical m alaria. This is especially true for forces deployed to highly-endemic areas in Africa and Southeast Asia where drug-resistant malaria is common. Methods:We conducted an outbreak investigation of malaria cases in Angola w here a total of 439 nonimmune Brazilian troops were deployed for a 6-month period in 1995-1996. A post-travel medical evaluation was also performed on 338 (77%) of the 439 soldiers upon return to Brazil. Questionnaire, medica l record, thick/thin smear,and serum anti-Plasmodium falciparum antibody ti ter (by IFA) data were obtained. Peak serum mefloquine (Mj and methylmefloq uine (MM) metabolite levels were measured in a subsample of 66 soldiers (42 cases, 24 nonmalaria controls) who were taking weekly mefloquine prophylax is (250 mg). Results: Seventy-eight cases of malaria occurred among the 439 personnel in itially interviewed in Angola (attack rate = 18%). Four soldiers were hospi talized, and 3 subsequently died of cerebral malaria. Upon return to Brazil , 63 (19%) of 338 soldiers evaluated were documented to have had clinical s ymptoms and a diagnosis of malaria while in Angola. in addition, 37 (11%) a symptomatically infected individuals were detected upon return (< 1% parasi temia). Elevated, post-travel anti-P. falciparum IFA titers (<greater than or equal to> 1:64) were seen in 101 (35%) of 292 soldiers tested, and was a ssociated with a prior history of malaria in-country (OR = 3.67 95% Cl 1.98 -6.82, p < .001). Noncompliance with weekly mefloquine prophylaxis (250 mg) was associated with a malaria diagnosis in Angola (OR = 3.75, 95% Cl 0.97- 17.41, p = .03) but not with recent P falciparum infection (by IFA titer). Mean peak levels land ratios) of serum M and MM were also found to be lower in those who gave a history of malaria while in Angola. Conclusions: Malaria was a significant cause of morbidity among Brazilian A rmy military personnel deployed to Angola. Mefloquine prophylaxis appeared to protect soldiers from clinical, but not subclinical, Fl falciparum infec tions. Mefloquine noncompliance and an erratic chemoprophylaxis prevention policy contributed to this large outbreak in nonimmune personnel. This repo rt highlights the pressing need for development of newer, more efficacious and practical, prophylactic drug regimens that will reduce the malaria thre at to military forces and travelers.