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Colombia experiencing an epidemic of cutaneous leishmaniasis
More children and women are affected as the parasite adapts to new regions; trials are underway for new treatment.
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Cutaneous leishmaniasis has reemerged in Colombia, particularly in pediatric patients in uncharacteristically peridomestic settings.
From 2002 to 2005, leishmaniasis cases in Colombia increased five-fold. Approximately 99% of these cases were cutaneous. Although most cases were reported among military personnel who have increased exposure to vectors, a higher number of women and children were also affected.
The reemergence of leishmaniasis in Colombia is due to the plasticity of Leishmania parasites who have adapted to new ecological settings, new vectors and new reservoirs, researchers said.
“This is concerning when you take into account the pathogenicity of leishmaniasis is greater in children and they are more likely to develop long-lasting, stigmatizing scars,” said Isabel Rodriguez, MD, a researcher from Centro Internacional de Enternamiento e Investigaciones Medicas (CIEIM) in Cali, Colombia and a first year PhD candidate at Johns Hopkins Bloomberg School of Public Health. “In many countries in South America, the numbers of patients who don’t respond to treatment is increasing.”
Rodriguez presented data on recent epidemiological trends, treatment failure in children and the emergence of resistance to leishmaniasis treatments at the 56th Annual Meeting of the American Society of Tropical Medicine and Hygiene, held recently in Philadelphia. Rodriguez and her colleagues at CIEIM are currently holding trials for efficacy of new leishmaniasis treatments in Cali and two other sites in Colombia.
Colombia epidemic peaks
Cutaneous leishmaniasis is contracted through the bite of a sandfly and is usually localized. Cases have now been reported in all regions (departments) of Colombia except for one. The average patient is a “working age” man; 70% of cases typically occur in men and the average age at presentation is 23.2 years. The average number of lesions per patient is 2.2. Treatment with pentavalent antimonials, the only available treatment in Colombia, is provided free by the government.
The epidemic in Colombia peaked in 2005. Chaparral, a municipality in Tolima, reported fewer than five cases each year until 2003 when the number of cases began increasing. In 2004, more than 1,500 cases were reported, representing the greatest leishmaniasis epidemic in Colombia. Case numbers have dropped in Chaparral, but have increased in nearby municipalities.
In Chaparral, the age and sex distribution of patients with cutaneous leishmaniasis is consistent with peridomestic transmission. More than 40% of cases occurred in women and girls and more than 30% of cases occurred in children younger than 12. Scientists noted different strains of Leishmania are emerging in new geolographical areas.
“Tropical rain forests highly contrast with Chaparral,” Rodriguez said.
The reemergence of Leishmania in Colombia has likely followed a typical model of urbanization and deforestation and the alteration of ecosystem, which has lead to the domestication of other vector-borne diseases, she said.
The armed conflict in Colombia, coupled with displaced populations and drug production and trafficking, also aids the spread of vector-borne infectious disease.
“A hypothesis shows that where the cocaine crops are grown, cases of leishmaniasis are increased,” Rodriguez said.
Pediatric treatment issues
In prior studies, children were less likely to respond to pentavalent antimonial treatment than adults. In a study to assess 10-day versus 20-day treatments, children younger than 5 years of age had a 25% response rate, which was much lower than the adult response rate. In the Chaparral epidemic, children younger than six had a 68% response rate to treatment, which was lower than children aged 6 to 15 years and adults.
The reason children have lower response rates is not known, but in a study conducted to assess pharmacokinetic differences in antimonials between children and adults, children aged 2 to 7 eliminated antimonials more rapidly than adults that resulted in a significantly lower exposure to the drug, Rodriguez said.
A trial is currently being conducted at three sites in Colombia. Children have been randomly assigned to antimonials or to miltefosine. Follow-up will continue for six months and outcome measures will be therapeutic response and adverse events.
Treatment resistance
In a study of the potential association of resistance and treatment failure, strains were isolated from 20 patients both at the time of treatment and at treatment failure. Nearly 20% of patients showed primary resistance and 20% showed secondary resistance. Researchers said results suggest that up to 40% of treatment failures may be due to resistant strains and that the selection of resistance may occur after a single course of treatment. – Kirsten H. Ellis
For more information:
- Rodriguez I. Current issues of cutaneous leishmaniasis in Colombia. Presented at: The 56th Annual Meeting of the American Society of Tropical Medicine and Hygiene; Nov. 4-8, 2007; Philadelphia