Case Report: Zoonotic Ancylostoma ceylanicum Infection Detected by Endoscopy

We report a case ofAncylostoma ceylanicum infection detected by endoscopy. It was diagnosed and confirmed using polymerase chain reaction (PCR) and DNA sequencing. The patient is a 58-year-old Malaysian woman who lives in a rural area, where uncontrolled populations of stray and semidomesticated dogs live in close proximity with humans. Hookworms are one of the most common parasitic nematodes that infect both humans and animals. The two primary species of hookworm infecting humans are Ancylostoma duodenale and Necator americanus. The public health impact of human hookworm infections is extensive, infecting an estimated 600 million people worldwide and resulting in up to 135,000 deaths annually. Other than the two anthropophilic species of human hookworms, cat and dog hookworms, such as A. ceylanicum, A. braziliense, and A. caninum, are also able to cause zoonotic disease in humans. The symptoms caused by zoonotic hookworms include creeping eruption, eosinophilic enteritis (EE), and less frequently, symptoms such as localized myositis, erythema multiforme, and ophthalmological manifestations. A. ceylanicum, however, is the only species of animal hookworm known to produce patent infection in humans. On November 11, 2013, a 58-year-old Chinese woman who presented with upper gastrointestinal (GI) bleeding (melena) was admitted to a private hospital for additional management. She was passing out black-colored stool one to two times per day for 1 week in early November of 2013. She was admitted to a local hospital for a similar problem before this admission. She had a few episodes of dizziness, tightness of chest, and cold sweats. There was no history of fever or weight loss. Laboratory investigations showed a hemoglobin concentration of 11.4 g/dL (11.5–16.5 g/dL), a platelet count of 169 k/mL (150–400 k/mL), a total white blood cell count of 8.0 k/mL (4.0–11.0 k/mL), neutrophils of 68% (40–75%), lymphocytes of 24% (20–45%), monocytes of 6% (2–10%), eosinophils of 1% (0–6%), and basophils of 1% (0–2%). Liver and renal functions were normal. The patient underwent oesophagogastroduodenoscopy (OGDS) and colonoscopy. Colonoscopy showed three polyps that were removed by polypectomy. Histopathological examination (HPE) showed them to be malignant. OGDS showed a gastric ulcer with signs of bleeding. Biopsy of the ulcer edge proved it to be malignant. Incidentally, a single adult blood-filled worm that measured 8–10 mm in size was seen moving on the duodenal mucosa (Figure 1). The worm was removed and sent to the Parasite Southeast Asia Diagnostic (Para:SEAD) Laboratory, Department of Parasitology, Faculty of Medicine, University of Malaya for species identification. Microscopic examination of the worm, including its buccal capsule or mouthpart, showed it to be an adult female hookworm (Figure 2). In addition, ova that were characteristic of hookworm species were seen in the ruptured uterus. Microscopic examination of the mouthpart was not clear and detailed enough to allow specific species identification. For specific species characterization, the worm was, therefore, subjected to polymerase chain reaction (PCR) targeted to the internal transcribed spacer-2 (ITS-2) ribosomal RNA gene as described previously. Briefly, the adult worm was ground with a sterile scalpel using mechanical vortex, and the homogenate was then digested with proteinase K followed by genomic DNA extraction using a commercial kit (MachereyNagel, Neumann-Neander, Duren, Germany). DNA amplification was performed, and the positive amplicon was subjected to DNA sequencing. Homology search using the National Center for Biotechnology Information (NCBI) reference sequences with Basic Local Alignment Search Tool (BLAST) confirmed the hookworm species as A. ceylanicum. A. ceylanicum is a hookworm species of dogs and cats. It is known to be endemic and widely distributed in Asia, especially southeast Asia. It is a neglected parasitic zoonotic nematode. Additional history revealed that the patient lives in a rural village, where uncontrolled populations of stray and semidomesticated dogs live in close proximity to human populations. In these rural settings, the close relationship shared with dogs, lack of veterinary attention, poor hygiene, and overcrowding contribute to a high risk of acquiring this zoonotic disease. A. ceylanicum is the only zoonotic species of hookworm known to infect humans, which was shown experimentally and naturally. Its contribution to human morbidity remains largely unexplored. It has always been regarded as a rare and uncommon parasitic infection. In fact, recent molecular-based surveys conducted mainly in southeast Asia, which included Malaysia, Thailand, and Laos, showed A. ceylanicum to be the second highest hookworm species infecting humans. There have been several clinical manifestations of A. ceylanicum infection in humans, and they were recently reviewed and summarized by Traub. In experimental infection of humans, clinical symptoms mimic the descriptions produced by anthroponotic hookworm species, including ground itch, abdominal pain, and GI discomfort. Although there are increasing reports of natural infections of A. ceylanicum in humans, unfortunately, in most of these cases, clinical information is limited or not available. Much like anthroponotic hookworm infections, patent infection with A. ceylanicum is capable of producing chronic infections, such as blood loss, and in high worm burden, it could lead to iron deficiency anemia. In recent years, the development and advancement in capsule endoscopy technologies that allow gastroenterologists *Address correspondence to Romano Ngui, Department of Parasitology, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia. E-mail: [email protected]