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Stool examinations showed numerous eggs (1–2 eggs/10 x 40 microscopic field) that were elongated and peanut-shaped with flattened bipolar plugs, striated shells (46.1 x 22.1 µm), and Charcot-Leyden crystals. Eggs were identified as those of C. philippinensis. Adult or larval C. philippinensis was not found in stool samples of all patients.
Levels of serum protein and albumin were low (1.7 and 0.9 g/dL, respectively), and proteinuria was not detected. A chest radiograph and abdominal ultrasound did not disclose any specific abnormalities. Gastroscopy showed a non-specific duodenitis with superficial erosions. A biopsy specimen of the duodenum did not show any parasites or specific abnormalities.
The patient reported eating small raw or insufficiently cooked fresh water fish and prawns in Lao PDR and Thailand. All other family members were healthy without any diarrhea. A routine stool examination performed for all family members showed negative results (no C. philippinensis eggs detected). The patient was given a one-month course of albendazole (400 mg/day) and he made uneventful and stable recovery.
Case 2 A 26-year old man from Vientiane. In December 2007, he came to the emergency department at Mahosot Hospital in Vientiane with a one-month history of profuse watery diarrhea. He was extremely emaciated and had severe prolonged dehydration. He was admitted for further investigations and treatment. During the preceding month, the patient had been repeatedly seen in district and military hospitals in Vientiane for the same symptoms. No diagnosis was made, including after stool examination, and multiple and empirical treatment regimens were given that did not relieve the symptoms.
He had approximately 10 bowel movements per day of non-dysenteric, watery stools associated with abdominal pain, borborygmus, anorexia, and episodic vomiting. The patient reported a weight loss of 13 kg within the past 4 weeks. He admitted eating raw fish. Other family members remained free of symptoms. Two months before admission, he had returned from central Thailand where he had been a migrant worker for approximately one year.
On physical examination, he appeared emaciated, pale, and in poor general health. He had subcutaneous fat and muscle wasting, marked pitting edema on the lower limbs, a temperature of 36°C, low blood pressure (80/50), a heart rate of 119 beats/minute, and a respiratory rate of 25 breaths/minute. The abdomen was distended. Results of chest and heart examinations were normal. The patient received intravenous fluids to correct dehydration and electrolyte imbalance. Stool examinations showed C. philippinensis eggs and parasitic co-infections (Table 1
). A chest radiograph and an abdominal ultrasound were normal. Stool examinations were carried out for all family members; none showed parasitic infections. After a full month course of albendazole (400 mg/day), the patient fully recovered. At a one-month follow-up visit, weight gain (8 kg), negative stool examination results, and normal levels of serum albumin were noted.
Case 3 A 27-year-old man (farmer) from southern Lao PDR (Phine District, Savannakhet Province). He was seen in September 2005 at Savannakhet Provincial Hospital with chronic diarrhea of six months duration. On admission, he had at least six daily bowel movements, persistent abdominal pain, and episodic vomiting. He was wasted and emaciated, moderately dehydrated, and reported a weight loss of 10 kg during the past 3 months.
The patient had no history of travel outside his province. After the start of illness, he visited district hospitals and a neighboring hospital in Vietnam where no diagnosis was made. Treatment with several anti-infective drugs, including ampicillin, sulfamethoxazole, and metronidazole, did not improve his condition. Results of stool examinations by the KatoKatz (KK) technique and a formalin-ether concentration technique (FECT) were positive for C. philippinensis (1,696 eggs/gram [of feces] [epg] by KK and 346 epg by FECT). Moreover, Opisthorchis viverrini (336 epg by KK and 58 epg by FET; 9 adult worms isolated after treatment with praziquantel and purgation), Strongyloides stercoralis (9 larvae), and hookworm (408 epg by KK and 14 epg by FECT) were also present. The patient received albendazole, 400 mg/day for 3 weeks, and showed gradual and significant improvement. He was lost to further follow-up.
The genus Capillaria is a nematode member of the superfamily Trichinelloidea, which includes Trichuris spp. and Trichinella spp.13 Among some 250 different Capillaria species, only three are human pathogens (C. hepatica and C. aerophila, which cause liver and a tracheo-bronchial disease, respectively, and C. philippinensis, which affects the intestinal tract). Capillaria philippinensis is the only species that causes severe disease. It may be endemic but also can cause epidemics.
The life cycle of C. philippinensis involves a small fresh water or brackish water fish harboring the infectious stages in their viscera. Natural definitive hosts are fish-eating birds. Human become infected when they consume raw or insufficiently cooked fish or, less often, ichtyophagic birds. Handling fish under poor sanitary conditions may contaminate other foods and favor indirect transmission.14 In humans, the parasite is not opportunistic (disseminated) but is usually restricted to the small intestine where it develops, reproduces, and where the female lays eggs that mature into larvae. A notable feature is that these larvae may engage in a shorten auto-infection circle, which may produce high parasitic loads.
The pathophysiology of this nematode is largely unknown, especially with regard to detail mechanisms of malabsorption. Parasitic products may interfere with ionic exchanges and carbohydrate and protein absorption of the intestinal epithelium, which produces a protein-losing enteropathy that is an outstanding feature of capillariasis.15,16
Intestinal capillariasis has been known since 1973 to occur in Lao-neighboring Thailand.3,17 It has been previously reported in travelers to Thailand.14 Two of our cases had stayed for several months in this country. This finding indicated that that they were infected in Thailand. However, one case from rural southern Lao PDR had no travel history out of this country. He must have been infected in Lao PDR, which documents that transmission of C. philippinensis infection also occurs in this country. Lao PDR and Thailand share many environmental, epidemiologic, and cultural features. In particular, the widespread habit of eating raw or insufficiently cooked fish, the main risk factor for infection with C. philippinensis, is common in both countries.
To our knowledge, the cases reported here are the first to be documented in Lao PDR. The patients were active healthy men with no underlying disease or immune deficiency. Clinical and laboratory features were comparable to those initially described in The Philippines2 and elsewhere, i.e. chronic watery diarrhea, abdominal pain, and notably pronounced weigh loss and pedal edema, the latter as part of a malabsorption syndrome. The diagnosis was easily achieved by finding ova of characteristic size and shape in stool specimens. However, C. philippinensis eggs may be sparse or inconstantly shed in the stools. They also have a similar appearance to those of T. trichiura in size and peanut shape with two polar opercula, and are often mistaken for those of the latter species.
The clinical presentation of capillariasis may be confused with those of other protozoans (Entamoeba histolytica), nematodes (S. stercoralis), trematodes (Fasciolopsis buski), or opportunistic parasites associated with acquired immunodefi ciency syndrome (Microsporidium spp.). In addition, capillariasis may be confused with other chronic diarrheas of unclear origin such as tropical sprue, collagen colitis, adult celiac, or Crohn disease. Associated hypovolemic cardiac failure has also been described.18 It is important to note that intestinal capillariasis even when properly recognized and treated recurs frequently because of auto-infestation or reinfection.
All three patients experienced clinical and biologic recovery (negative stool results for parasites, serum albumin levels returning to normal values) after completing the 3–4-week regimen of albendazole. To avoid frequent relapses, high dosages and prolonged (3–4 weeks) or sequential treatments have been advocated.19 Several anti-helminthic drugs have been recommended for treatment of intestinal capillariasis. All compounds of the azole family of drugs are effective. However, several studies7,13,19–22 have consistently recommended albendazole as the drug of choice.
Unawareness and delayed diagnosis may cause serious medical problems. This issue has been documented in South Korea, Egypt, and India, and may even be fatal (fatality rate up to 30% in an outbreak in The Philippines), which is an exceedingly uncommon outcome for other nematode infections.5,10,16,23,24
Finally, food-borne parasites are an emerging public health problem, particularly in Southeast Asia.25 Intensified production of fish farming and the persisting habit of eating raw or undercooked fresh water fish contribute to increased transmission rates, including Capillaria spp.1,4,6,26 As an example, in Lao PDR, despite increased development, as many as 75% of the population still eat traditional raw fish dishes27 such as Koy kung (prawn), koy pa or lap pa (minced fish with spices), and koy pa siew (raw Rasbora borapetenis). Therefore, C. philippinensis deserves particular attention in this and neighboring countries that have similar environments and traditional behavior patterns. Because this parasite is endemic in this region, the occurrence of outbreaks cannot be excluded.
Received April 5, 2008. Accepted for publication June 25, 2008.
Acknowledgments: We thank the patients, and doctors, laboratory staff, and infectious ward staff at Setthathirath Hospital, Mahosot Hospital, Savannakhet Provincial Hospital, and the Department of Parasitology, University of Health Sciences, Vientiane, Lao PDR, for their participation in the study.
Financial support: This study was supported by the Swiss National Science Foundation and Swiss Agency for Development and Cooperation (project no. NF3270B0-110020), the Canton of Basel-Stadt, Switzerland, and the Institut de la Francophonie pour la Médecine Tropicale, Vientiane, Lao PDR.
* Address correspondence to Peter Odermatt, Department of Public Health and Epidemiology, Swiss Tropical Institute, PO Box, CH-4002 Basel, Switzerland. E-mail: peter.odermatt{at}unibas.ch 
Authors’ addresses: Phonepasong Soukhathammavong and Somphou Sayasone, National Institute of Public Health, Ministry of Health, Vientiane, Lao PDR and Department of Public Health and Epidemiology, Swiss Tropical Institute, Basel, Switzerland. Aina Nirina Harimanana, Aphonethip Akkhavong, and Michel Strobel, Institut de la Francophonie pour la Médecine Tropicale, Vientiane, Lao PDR. Sivilay Thammasack and Simmaly Phongmany, Department of Infectious Medicine, Mahosot Hospital, Ministry of Health, Vientiane, Lao PDR. Niranh Phoumindr, Department of Parasitology, University of Health Sciences, Vientiane, Lao PDR. Khamloun Choumlivong and Khamla Choumlivong, Department of Internal Medicine, Setthathirath Hospital, Ministry of Health, Vientiane, Lao PDR. Valy Keoluangkhot, Department of Infectious Medicine, Mahosot Hospital, Ministry of Health, Vientiane, Lao PDR and Institut de la Francophonie pour la Médecine Tropicale, Vientiane, Lao PDR. Kongsap Akkhavong, National Institute of Public Health, Ministry of Health, Vientiane, Lao PDR. Christoph Hatz and Peter Odermatt, Swiss Tropical Institute, Basel, Switzerland.
Reprint requests: Peter Odermatt, Department of Public Health and Epidemiology, Swiss Tropical Institute, PO Box, CH-4002 Basel, Switzerland, Tel: 41-61-284-8214, Fax: 41-61-284-8105, E-mail: peter.odermatt{at}unibas.ch.
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