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Adults who have not grown up in a malaria-endemic area may experience severe malaria soon after entering a malarious area. Such mortality is usually limited to a short period of time (months), after which they are thought to be "immune." Such anti-disease immunity may be more accurately considered as tolerance. Malaria rates of British soldiers during the Second World War reflected their time with suppressed infections and the transmission levels. Black workers from non-endemic areas on the Panama Canal experienced higher initial mortality and infection rates than co-located white workers for Plasmodium falciparum, whereas the known genetic resistance of blacks to Plasmodium vivax reversed these rates. The ethnic differences observed in malaria rates may have more to do with acquired tolerance than genetic resistance. Long-term (years) sub-patent infections may maintain host tolerance, and elimination of malaria infections may place these adults at subsequent risk of severe malaria.

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An entomologic search was carried out to collect intradomicile triatomines in dwellings from rural communities in the western border of the Panama Canal, Panama. Sixty-nine triatomines were collected inside 20 houses of 67 houses investigated. Rhodnius pallescens was the only triatomine species found and included adults of both sexes and nymphs. A significantly high Trypanosoma cruzi (72.7%) and T. rangeli (40%) vector infection rate was detected. Blood meal analysis showed that 68% of R. pallescens had fed on humans. Human serologic analysis and hemoculture performed on inhabitants from triatomine-infested houses showed that 32.1% (18 of 56) of the samples were trypanosome infected. Thirteen samples (23.2%) had antibodies against T. cruzi. Six of these seropositive samples were from children less than 15 years old. Trypanosoma rangeli was isolated in five hemoculture samples, all from children less than 11 years old. The epidemiologic implications of these findings in terms of human infection are discussed.

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The eco-epidemiology of T. cruzi infection was investigated in the Eastern border of the Panama Canal in Central Panama. Between 1999 and 2000, 1110 triatomines were collected: 1050 triatomines (94.6%) from palm trees, 27 (2.4%) from periurban habitats and 33 (3.0%) inside houses. All specimens were identified as R. pallescens. There was no evidence of vector domiciliation. Salivary glands from 380 R. pallescens revealed a trypanosome natural infection rate of 7.6%, while rectal ampoule content from 373 triatomines was 45%. Isoenzyme profiles on isolated trypanosomes demonstrated that 85.4% (n = 88) were T. cruzi and 14.6% (n = 15) were T. rangeli. Blood meal analysis from 829 R. pallescens demonstrated a zoophilic vector behavior, with opossums as the preferential blood source. Seroprevalence in human samples from both study sites was less than 2%. Our results demonstrate that T. cruzi survives in the area in balanced association with R. pallescens, and with several different species of mammals in their natural niches. However, the area is an imminent risk of infection for its population, consequently it is important to implement a community educational program regarding disease knowledge and control measures.

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A epidemiologia da infecção do T. cruzi foi investigada na margem oriental do canal do Panamá, na região central da Republica do Panamá. A informação obtida durante o estudo avaliou fatores de risco da doença de Chagas nesta área. Entre 1999 e 2000, 1110 triatomíneos foram coletados: 1050 triatomíneos (94,6) em palmeiras, 27 (2,4) em habitats periurbanos e 33 (3,0) no interior de casas. Todos os espécimens foram identificados como R. pallescens. Não havia nenhuma evidência de domiciliação do vetor. O exame de glândulas salivares de 380 R. pallescens revelaram taxa de infecção natural por Trypanosoma de 7,6, mas o conteúdo da ampola rectal de 373 triatomíneos mostrou 45 de positividade. Os perfis de isoenzimas em Trypanosomas isolados demonstraram que 85,4 (n = 88) eram T. cruzi e 14,6 (n = 15) eram T. rangeli. A análise da refeição de sangue de 829 R. pallescens demonstrou comportamento zoofílico do vetor, sendo os gambás a fonte preferencial de sangue. Soroprevalência nos seres humanos de ambos locais de estudo foi menos que 2. Nossos resultados demonstram que T. cruzi sobrevive na área em associação equilibrada com R. pallescens e com diversas espécies diferentes de mamíferos em seus nichos naturais. Entretanto, a área é um risco eminente de infecção para sua população, pelo que é importante executar um programa educacional na comunidade a respeito das medidas, do conhecimento e do controle da doença.

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An outbreak of cutaneous leishmaniasis occurred in a unit of 608 Puerto Rican national guardsmen conducting jungle warfare training in the Panama Canal Area in July 1984. An epidemiologic investigation of reported nonhealing, ulcerating skin lesions was conducted among 540 (89%) unit members in November and December 1984. Fifteen (88%) of 17 individuals with chronic, ulcerating skin lesions were confirmed as cases of cutaneous leishmaniasis by culture or histopathology. Twelve cases yielded positive Leishmania cultures, identified as L. braziliensis panamensis by cellulose acetate electrophoresis. Evaluation of different diagnostic techniques revealed that direct examination of tissues by Giemsa-stained histological examination was the most sensitive test (87% sensitivity), with an indirect immunofluorescent antibody test being rather insensitive (67%). All but one of the confirmed cases operated in small units that trained and slept overnight at a mortar firing site for a period of three days, yielding a site-specific attack rate of 22% (14 of 64). This contrasted with a much lower attack rate of 0.2% (1 of 476), experienced by unit members who trained at other locations during the same time frame (P less than 0.001). The median incubation period calculated from day of arrival at the mortar firing site was 17 days (range 2-78) for the 15 confirmed cases. Available personal protection methods, such as the use of insect repellents, were not appropriately implemented by unit personnel and thus, were not found to effectively protect against Leishmania infection. This is the largest reported outbreak of cutaneous leishmaniasis in military personnel associated with a single geographic focus of infection and contrasts with the usual sporadic disease experience in Panama.

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Narrativa historica que comenta a experiencia francesa de 1881 a 1890 em relacao a construcao do Canal do Panama, onde a febre amarela e a malaria causaram estragos entre os trabalhadores, e a atuacao das forcas de ocupacao dos Estados Unidos no saneamento de Havana, inclusive redimensionando o abastecimento de agua

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