Venezuelan equine encephalitis--Colombia, 1995.
Authors: E Daza, V Frias, A Alcola, I Lopez, I Bruzon, JT Montero, G Alvarez, MA Garcia, R Rodriguez, J Boschell, F de la Hoz, F Rivas, V Olano, LA Diaz, FM Caceras, G Aristizabal, V Cardenas, J Cuellar, E Gonzalez, A Ruiz, F Pinheiro, R Gusmao, S Weaver, R Tesh, R Ricco-Hesse
Journal: MMWR Morbidity and Mortality Weekly Report (1995)

An outbreak of Venezuelan equine encephalitis (VEE) that began in northwestern Venezuela in April 1995 has spread westward to the Guajira peninsula and to Colombia (Figure 1), resulting in an estimated minimum of 13,000 cases in humans and an undetermined number of equine deaths. Governments of both countries have initiated efforts to control the spread of this outbreak by quarantining and vaccinating equines and applying insecticides. This report summarizes the ongoing investigation of the outbreak in Colombia.



FIGURE 1

Location of outbreak of Venezuelan equine encephalitis — Colombia, April 1–October 1, 1995



During the first week of September, rural health clinics in the towns of Mayapo, Manaure, and El Pajaro in the municipality of Manaure in La Guajira state reported an increased number of patients seeking care for acute febrile illnesses characterized by intense headache, muscle pain, prostration, and vomiting. Illness in some patients was complicated by convulsions and other neurologic symptoms.

As of September 28, a total of 8320 persons with acute febrile illness compatible with VEE had been treated at public hospitals and clinics in La Guajira, and large outbreaks had been reported from the towns of Manaure, Riohacha, El Pajaro, Mayapo, Uribia, and Meicao. Based on a random survey of 250 residents of Manaure, a recent history of acute illness compatible with VEE was present in 57% of respondents (Figure 2); 4% reported associated convulsions, and one person died (case-fatality rate=0.7%). All age groups were equally affected. In Manaure, the epidemic peaked on September 19, and malathion spraying was initiated on September 21.



FIGURE 2

Number of Venezuelan equine encephalitis cases estimated from a random household survey (n=250), by date of onset — Manaure,* Colombia, September 1–26, 1995



In Riohacha, the state capitol, hospital visits for acute febrile illness increased steadily in September, reaching 143 visits on September 24 with no evidence of a decline. A similar pattern occurred in Uribia. Based on interviews and physical examinations of 23 inpatients at local hospitals on September 27–28, prominent manifestations included fever (100%); convulsions (98%); headache (56%); photophobia (56%); myalgias (56%); and chills, vomiting, and diarrhea (48% each). Ten associated deaths were reported statewide. Unidentified viral isolates have been recovered from four of 18 human blood samples submitted to the Colombian National Institute of Health.

Because of a prolonged rainy season (the heaviest in 20 years in La Guajira), mosquito abundance has increased dramatically. Aedes aegypti house indices increased in August to 70% in Manaure and to 22% in Riohacha. Entomologic surveys in Manaure detected large numbers of Psorophora confinnis and Ae. taeniorhynchus breeding in estuarine waters in the town’s vicinity. The equine population in La Guajira consists of approximately 70,000 unvaccinated horses, donkeys, and mules owned by native Wayuu people, who constitute approximately 35% of the inhabitants of Riohacha. Control measures instituted by the government of Colombia include vaccination of equines in La Guajira, restriction of equine movement from and within the state, large-scale application of insecticides, public education and community mobilization campaigns to eradicate mosquito breeding sites, issuance of guidelines on case-management and referral, and surveillance of humans and equines.