Ancylostoma ceylanicum is a parasitic roundworm, commonly known as a hookworm, that primarily inhabits the small intestine of its hosts. Unlike most animal hookworms, it can cause symptomatic infections in humans. This species infects both humans and various mammals, including dogs and cats.
Transmission Pathways
Transmission begins when eggs are passed in the feces of an infected host into the environment. Under suitable conditions like moisture, warmth, and shade, these eggs hatch in one to two days. The hatched rhabditiform larvae grow in feces or soil, molting twice over five to ten days to become infective filariform larvae. These larvae can survive in favorable conditions for three to four weeks.
Humans and animals primarily acquire infection through direct contact with contaminated soil, often by walking barefoot, allowing larvae to penetrate the skin. Once inside, larvae enter blood vessels, travel to the heart and lungs, ascend to the pharynx, are swallowed, and reach the small intestine to mature. Oral ingestion of infective larvae, such as through contaminated food or water, also leads directly to the small intestine for maturation.
Signs of Infection
Infection with Ancylostoma ceylanicum can manifest with various signs and symptoms, depending on the host and the worm burden. In humans, initial exposure to larvae penetrating the skin can cause an itchy, red rash known as “ground itch” at the entry site. As adult worms establish themselves in the small intestine, they attach to the intestinal wall and feed on blood, which can lead to gastrointestinal symptoms like abdominal pain, loss of appetite, and diarrhea.
A primary consequence in humans is iron-deficiency anemia, resulting from chronic blood loss due to the worms feeding in the small intestine. Each adult hookworm can cause an estimated blood loss of 0.3 to 0.5 mL per day. This anemia can lead to fatigue, weakness, shortness of breath, and pale skin. In children, persistent blood loss may result in severe anemia, potentially leading to impaired growth, cognitive development, and in severe cases, heart failure.
Animals, particularly dogs and cats, also exhibit signs of infection. Anemia is a prominent clinical sign, often indicated by pale gums and general weakness. Other gastrointestinal symptoms include weight loss, decreased appetite, vomiting, and diarrhea, which may sometimes contain fresh blood or appear dark and tarry due to digested blood. In young animals like puppies and kittens, severe infections can be life-threatening and may lead to poor growth or even death.
Global Presence
Ancylostoma ceylanicum is primarily found in tropical and subtropical regions across the globe. Its prevalence is particularly high in parts of Asia, including Southeast Asia, where it is recognized as a significant cause of zoonotic hookworm infection in humans. Beyond Asia, this hookworm is also endemic in areas of Africa and Australia. Recent studies have also identified autochthonous infections in the Americas, such as in Ecuador and Grenada in the Caribbean.
The environmental conditions in these regions contribute to the parasite’s life cycle and transmission. Warm, moist soil provides an ideal habitat for the eggs to hatch and for the larvae to develop into their infective stage. Areas with inadequate sanitation and close contact between humans and infected animals, such as free-roaming dogs and cats, further facilitate the spread of Ancylostoma ceylanicum. The persistence of larvae in contaminated soil for several months enables its widespread presence.
Addressing and Avoiding Infection
Diagnosis
Diagnosis typically involves examining stool samples for hookworm eggs. Microscopic identification of these eggs is the most common method. The procedure includes collecting a stool specimen, fixing it in formalin, and concentrating the sample using techniques like formalin-ethyl acetate sedimentation to improve detection. While conventional stool examinations are the gold standard, molecular methods such as PCR may be used for more accurate species identification when egg counts are low.
Treatment
Treatment for Ancylostoma ceylanicum infection in both humans and animals involves anthelmintic medications. For humans, commonly prescribed drugs include albendazole and mebendazole. Albendazole is often administered as a single 400 mg oral dose, while mebendazole can be given as a 100 mg dose twice daily for three days or a single 500 mg dose. These medications work by blocking the parasite’s microtubule functions, inhibiting glucose uptake, and leading to a shortage of glycogen, which ultimately starves the worms. It is important to consult a medical professional for appropriate dosage and treatment plans, especially for children or pregnant women.
For infected animals, various anthelmintics are available, including fenbendazole, moxidectin, pyrantel, and milbemycin. For cats, specific treatments like emodepside, eprinomectin, and selamectin are also used. Prompt veterinary consultation is recommended to determine the correct medication and dosage for pets, as drug resistance in some hookworm species is an emerging concern. Beyond medication, supportive care, such as iron supplementation for anemia and nutritional support, may be necessary for both humans and animals, particularly in cases of heavy or chronic infection.
Prevention
Preventing Ancylostoma ceylanicum infection involves improved sanitation and reduced exposure to contaminated environments. Proper disposal of human and animal feces is a primary preventive measure to limit egg spread into the soil. Wearing shoes, especially in tropical and subtropical areas, reduces the risk of larvae penetrating the skin. Covering children’s sandboxes when not in use also prevents larvae from developing.
Regular deworming programs for pets, particularly in endemic areas, are effective in reducing eggs shed into the environment. Avoiding contact with potentially contaminated soil, especially where free-roaming animals are present, further minimizes infection risk. Public health education on hygiene practices, such as thorough handwashing after contact with soil or animal feces, also helps prevent human infections.