The Extent of Paragonimiasis Infections

Abstract & Commentary

Synopsis: Thirty years ago, I graduated from Cornell Medical College and took leave of the Upper East Side in New York City for a summer fellowship in tropical medicine under the auspices of Louisiana State University. I was placed in Medellin, Columbia, with a wonderful mentor and scholar, Dr. David Botero, at the University of Antiochia. With his considerable personal expertise and the rich medical culture of Andean Colombia, I found myself in the perfect environment in which to learn practical parasitology and clinical tropical medicine. As we enter the 21st century, Velez and associates from that institution now report their findings of endemic paragonimiasis in Colombia.

Source: Velez B ID, et al. Epidemiology of paragonimiasis in Colombia. Trans R Soc Trop Med Hyg. 2000;94(6): 661-663.

Despite fantastic clinical experiences in the diagnosis and treatment of intestinal protozoa and helminth infections while working in Colombia, South America, there was no way to see it all. In fact, one parasitic disease was not even considered in Colombia at that time, even when working with potential cases of pulmonary tuberculosis. That disease was paragonimiasis, which was not known to be endemic in Colombia during the 1970s. By 1993, only 3 cases had been described as originating from that part of South America, and all were described in the local professional literature, therefore not well known outside Colombia. This current report from the University of Antiochia’s Tropical Disease Program extends the known endemic foci of paragonimiasis and serves to remind travel medicine consultants that paragonimiasis is simply not confined to Asia. Nor should it any longer be referred to as the "oriental lung fluke."

An epidemiological study of paragonimiasis in Colombia was motivated by the diagnosis of this disease in an aboriginal Embera tribe member treated in Medellin after paragonimiasis was diagnosed on sputum examination for ova. Further investigation into several indigenous settlements of the Embera people on the Colombian Pacific coast (see Figure) identified 24 new human cases of infection.

The 5 Embera communities are located in remote jungle regions that lack easy accessibility. Each contains about 100-300 individuals. Huts are built along creeks or rivulets, and, traditionally, the Embera will defecate into these waters, where they also bathe and wash their clothing daily. Water for preparation of food is taken from the same sources. Five communities were surveyed, first using voluntary participation for stool collections. Those who were symptomatic (ie, showing respiratory symptoms or reporting hemoptysis) were subjected to clinical evaluation and direct sputum examinations. Some of these symptomatic patients received radiographic or computer-assisted tomographic chest evaluations. To determine previous exposure and infection rates in the community, an intradermal skin test (paragonimin antigen) was used to determine immediate hypersensitivity. Actively infected patients were treated with praziquantel at an oral dose of 75 mg/kg/d for 3 days. Responses were evaluated by follow-up stool examinations both 5 and 12 months after treatment.

A total of 24 new human cases were identified in the Embera communities, all within the departments of Antioquia and Chocó. Most were younger than age 14, and raw crab consumption was their common characteristic exposure to this infection. Cough (100%), hemoptysis (88%), thoracic pain, and mild dyspnea (22%) were the most frequent symptoms. Chest radiography was normal in 1 patient; it showed upper lobe cavities in 2 others but was otherwise nonspecific. The most frequent radiographic findings were cystic areas or "cotton-like" infiltrates.

In Medellin, the laboratory of the Program for the Study and Control of Tropical Diseases performed examinations of mollusks and crustaceans obtained from fresh-water ecosystems located near the Embera huts. The first intermediate host was identified as a snail, Aroapyrgus spp. The second intermediate host was a newly identified crab species named Hypolobocera emberarum. Intermediate hosts were found in the decaying vegetation and herbaceous plants growing on the banks of rivulets that the communities used as latrines.

Comment by Frank J. Bia, MD, MPH

The presence of paragonimiasis foci within tropical regions of the Americas, extending from Mexico to Brazil, has been known for many years. Cornejo and colleagues recently published their data on the examination of crab intermediate hosts for paragonimiasis in 2 Peruvian districts. Of 120 freshwater crabs, 17.5% (21) of those examined were infected with Paragonimus mexicanus. Fecal and sputum samples from 409 preschool and school children in these districts were examined for ova, and 2 infected children were identified.¹

In North America, Procop and associates reported a 21-year-old male who developed hemoptysis caused by infection with P kellicotti acquired by ingesting local infected crayfish. The presence of Paragonimus spp. in North America has been known for more than 100 years. This patient was infected after catching and eating crayfish caught in a tributary of the Arkansas River during a camping trip. Infection occurred about 6 months prior to the onset of symptoms. The crayfish were incompletely cooked in an attempt to roast them over an open fire in the evening. Characteristic ova were identified in cytologic preparations obtained from bronchoalveolar lavage fluid.² Cytology technicians working with lavage fluid may encounter the ova of various Paragonimus spp. as part of their cytologic examination of sputum for malignant cells or microbial pathogens.

Japanese surgeons recently reported being referred 7 adult males, nearly all older than age 50, with mass lesions on chest radiographs that were indistinguishable from malignancies. Only 1 had a high circulating eosinophil count. Half these patients had ova detected in transbronchial lung biopsies, and all had a positive serology for Paragonimus-specific IgG antibodies.³ From 1986 to 1998, 104 cases of paragonimiasis were identified in Miyazaki Medical College, Kiyotake, Japan. Chest radiographs were abnormal in 80%; ova were detected on sputum examinations in about 50%. Eosinophilia and/or elevated serum IgE levels were present in about 80%. Paragonimiasis is actually felt to be a re-emerging public health problem in the southern island of Kyushu, Japan.⁴

Infection is acquired when humans ingest raw meat or viscera of the second intermediate host, a freshwater crustacean. The 3 cases of paragonimiasis originally described in Colombia during the 1980s were not identified in the indigenous populations of that region but, rather, among inhabitants of the inter-Andean valleys and eastern Colombia. The practice of defecating into streams where intermediate hosts are present is common throughout the developing world, and it should not be surprising that paragonimiasis foci have been identified when sought with appropriate investigations. More than 30 species of Paragonimus are said to infect humans. Adult flukes live within lung parenchyma but may also migrate to brain. Their life span is about 5 years.

For travel medicine consultants, it will be important to widen their scope of diagnostic considerations to include less familiar geographic distributions of paragonimiasis.⁵ The Columbian authors appropriately point out that the disease is found throughout parts of tropical and subtropical Africa, Asia, and the Americas. Paragonimiasis might simulate tuberculosis on chest radiography and cause diagnostic confusion since hemoptysis is characteristic of both diseases. In the recent past, young patients (often refugees arriving from endemic areas of Asia with neither evidence for active tuberculosis nor a positive PPD skin test) would be quickly evaluated for active paragonimiasis. The general awareness in the medical community of similar clinical presentations for both diseases was at a fairly high level during the migrations from southeast Asia to the rest of the developed world in the late 1970s. Sputum and stool examination for ova of Paragonimus spp. and serology for paragonimiasis prevents such cases from being missed, particularly if infections occur in patients from geographic areas that are not generally considered endemic for this disease. In addition, a recent outbreak of leptospirosis among participants in remote competitive adventure travel (see Hill DR. Travel Medicine Advisor Update. 2000;10:41-43) clearly should remind us that the quest for such experiences can lead us far afield. The chances that groups of such travelers would encounter unfamiliar areas of paragonimiasis endemicity are now increasing.

The first species of Paragonimus reported from Columbia was P caliensis in 1968. However, the current study has likely identified a new and different species. Among the Embera peoples, the consumption of raw crabs is felt to bestow the characteristics of that species upon those who consume them. In this case, the men might become better hunters and skilled fighters. Whether the desired traits are acquired, raw crabs do pass on one of their defining ecological characteristics to those who consume them, namely paragonimiasis.

References

1. Cornejo W, et al. Paragonimosis in the Cajabanba and Condebanba districts, Cajamarca, Peru. Rev Inst Med Trop Sao Paulo. 2000;42:245-247.

2. Procop GW, Marty AM, Scheck DN, et al. North American paragonimiasis. A case report. Acta Cytol. 2000;44:75-80.

3. Tomita MM, et al. Pulmonary paragonimiasis referred to the Department of Surgery. Ann Thorac Cardiovasc Surg. 2000;6:295-298.

4. Uchiyama F, Morimota Y, Nawa Y. Re-emergence of paragonimiasis in Kyushu, Japan. Southeast Asian J Trop Med Public Health. 1999;30:686-691.

5. Hawn TR, Jong EC. Update on hepatobiliary and pulmonary flukes. Curr Infect Dis Rep. 1999;5:427-433.