When Parasites Travel

Mobile population importation of drug-resistant infections and diseases is a focus of the November 2009 issue of Emerging Infectious Diseases. In that issue, MacPherson and colleagues cite, “Many examples of imported multidrug-resistant (MDR) infectious diseases are associated with migrant populations, e.g., MDR Plasmodium falciparum malaria in immigrants, tourists, and returned foreign-born travelers.”

Parasites travel –

  • According to Monge-Maillo, malaria accounted for nearly 10% “of 2,198 immigrants referred to the Tropical Medicine Unit of Ramón y Cajal Hospital over a 20-year period” in Spain.
  • CDC received reports of 1,324 cases of malaria, including four fatal cases, with an onset of symptoms in 2004 among persons in the United States or one of its territories. This number represents an increase of 3.6% from the 1,278 cases reported for 2003,” as reported in MMWR by Skarbinski and colleagues.
  • In the Netherlands 5043 laboratory cases of imported malaria were confirmed between 2000 and 2003 according to Klein and Bosman.

fly_dscn0185.JPGThe problem is worse when drug-resistant parasites travel. Chan and co-researchers have been examining archival human sera “to explore the origin and evolution of Plasmodium falciparum chloroquine resistance in the Pacific.”

In 2002 Afghan refugees brought malaria into northwestern Pakistan. They experienced a 28% treatment failure rate when chemically substandard locally manufactured sulfadoxine-pyrimethamine was used for routine treatment. This is a potential way of producing drug resistance that could be carried back home by returning refugees

MacPherson and colleagues demand what they call, “Pharmaceutical security systems for standard and quality medicines,” in an effort to combat “commonly substandard or counterfeit” drugs in endemic countries.  Progress in eliminating malaria in Zanzibar, Rwanda and Zambia can easily be threatened if resistant parasites cross their borders. These parasites don’t need passports and visas.

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