Parasites Going Global
Parasites Going Global
Abstracts & Commentary
Synopsis: Recent publications update our knowledge of the transmission and geography of parasitic diseases. In Europe, eating undercooked meat (rather than having contact with cats and cat litter) accounts for most of the risk of toxoplasmosis. In addition, two travelers to Ireland ate raw watercress and inadvertently came home infected with Fasciola hepatica, a liver fluke. Care with food selection is important for all travelers, even those with itineraries including only developed countries in temperate regions.
Sources: Cook AJC, et al. Sources of toxoplasma infection in pregnant women: European multicentre case-control study. BMJ 2000;321:142-147; LaPook JD, et al. Sheep, watercress, and the internet. Lancet 2000;356:218.
Toxoplasmosis causes significant morbidity in children born to women who are infected with Toxoplasma gondii during pregnancy. A collaborative group of European investigators determined the relative importance of various food and environmental risk factors for acute gestational toxoplasmosis. A total of 252 infected women and 858 control women were enrolled and interviewed in six European cities (Naples, Lausanne, Copenhagen, Oslo, Brussels, and Milan). Statistically, eating undercooked meat accounted for 30-63% of infection in the different centers while 6-17% of infections related to contact with soil. Less than 10% of infections were associated with travel outside of Europe and North America. Neither contact with cats nor cat litter was associated with a clear risk of infection. Cook and colleagues suggest that consumers should be better informed about the risk associated with undercooked meat.
A 65-year-old man and his 61-year-old wife returned to the United States from Ireland. A month later, the man developed fever and weight loss with elevated serum liver enzyme concentrations and peripheral blood eosinophilia (15%). A month later, the wife also developed eosinophilia (45%) and liver enzyme elevations. Internet communications and multi-national collaboration led to specific Fasciola serological testing by indirect immunofluorescence and counter immunoelectrophoresis; results were strongly positive for each of the individuals. Triclabendazole was given orally, and each subject recovered fully. LaPook and associates state that "with worldwide travel increasingly common, this case illustrates the importance of thinking globally."
Comment by Philip R. Fischer, MD, DTM&H
The field of travel medicine is growing and gaining importance as international travel becomes increasingly feasible. It is not only presidents and congressional delegations that can visit multiple African countries in the course of a long weekend. The infectious risks of international travel, however, are not limited to visitors to tropical areas or to less developed countries.
West Nile virus has made a second annual appearance in New York City, and two individuals actually contracted malaria in New York’s Suffolk County last year.1 Clearly, exotic viruses and "tropical" parasites can thrive and cause human infection in temperate areas.
The two reports summarized here remind us that careful attention to hygienic food choices is important, even for travelers to Europe. Obviously, it’s not just in Europe where we should be careful about incompletely prepared food. The 1971 medical school class at Cornell unwittingly became subjects of an outbreak of toxoplasmosis when they ate undercooked hamburger.2 Residents and travelers in most countries should avoid unclean raw vegetables and uncooked meat.
The incidence of positive toxoplasma serology in pregnant European women varies from 10% in some northern countries to 55% in France and Greece. Some women become infected during pregnancy, and 0.01-0.1% of European babies have congenital toxoplasmosis. A few of these children die, others develop learning difficulties, and many develop eye lesions leading to permanent visual impairment. Prevention of infection rests on avoidance measures, but avoidance depends on an understanding of the risks and routes of infection. Common "knowledge" suggests that pregnant women should avoid cats and cat litter, but the current study shows that cats are not a clear risk factor for most European women. Instead, pregnant women should emphasize avoiding consumption of raw, undercooked, and undercooked meat. Travel medicine practitioners should include reminders to avoid incompletely prepared meat when counseling travelers to Europe, especially pregnant travelers.
Fasciola hepatica had not been known to cause human disease in Ireland for approximately four decades. The visiting Americans cited above had apparently picked some watercress growing near a river and incorporated it into sandwiches. The ingested immature flukes on the fresh food left the travelers with more memories than just those of idyllic pastoral scenes of the Irish countryside. Each of us would do well to remember not to eat foods that might have been fecally contaminated by sheep and other animals.
How do these reports affect our practice of travel medicine? First, we are reminded to inform travelers even to industrialized countries to avoid unclean fresh foods and incompletely cooked meats. Second, we must be vigilant with broad differential diagnoses when treating patients with unusual presentations as "exotic" infections, like travelers, are increasingly going global.
References
1. Probable locally acquired mosquito-transmitted Plasmodium vivax infection—Suffolk County, New York, 1999. MMWR Morb Mortal Wkly Rep 2000;49:495-498.
2. Kean BH, Kimball AC, Christenson WN. An epidemic of acute toxoplasmosis. JAMA 1969;208:1002-1004.
Editor’s Note
Having been a member of the class of 1971 at Cornell Medical College, I was involved in the toxoplasmosis outbreak mentioned by Phil Fischer in his commentary. It was one of the first outbreaks to be clearly associated with undercooked meat, but it was a different era—one in which there were few women in medical school. Had there been an outbreak among our current students at Yale, in which half of the class are women, the real possibility of toxoplamosis during pregnancy would have occurred. We talk extensively to our patients about risk factors for this disease during pregnancy, but it is clear that for our patients who are traveling while pregnant we must caution them about the major risk factor—undercooked meat.
Subscribe Now for Access
You have reached your article limit for the month. We hope you found our articles both enjoyable and insightful. For information on new subscriptions, product trials, alternative billing arrangements or group and site discounts please call 800-688-2421. We look forward to having you as a long-term member of the Relias Media community.