HOOKWORMS (1 CE Hour) Learning objectives ! List the risk factors for hookworm infections. ! Explain how and where humans and animals can become infected. ! Explain how to diagnose, treat and prevent hookworm infection. ! Describe the life cycle of these parasites. ! List recommendations you can provide to pet owners about treatment and prevention. ! List the contraindications when prescribing medications for hookworm. Introduction Zoonoses are infectious diseases that can be transmitted from animals to humans, most likely when animals and human beings are in close contact. Causative groups of agents include parasites, fungi, bacteria, viruses. Usually of minor importance, they nevertheless can lead to severe disease, especially in the very young and those with certain conditions, and to death, particularly with certain viral diseases (such as rabies, hemorrhagic fevers, encephalitis). Hookworms exist worldwide and Life cycle (Intestinal hookworm infection) cross from carnivorous animals to man in all Eggs are passed in the stool , and under favorable conditions (moisture, warmth, shade), larvae parts of the world. hatch in one to two days. The released rhabditiform larvae grow in the feces and/or the soil , and The parasite after 5 to 10 days (and two molts) they become filariform (third-stage) larvae that are infective . These infective larvae can survive three to four weeks in favorable environmental conditions. On Hookworms belong to the family of contact with the human host, the larvae penetrate the skin and are carried through the blood vessels to Ancylostomatidae which are part of the the heart and then to the lungs. They penetrate into the pulmonary alveoli, ascend the bronchial tree to Phylum of Nematodes: Ancylostoma caninum the pharynx and are swallowed . The larvae reach the small intestine, where they reside and mature and A. braziliense (dog, fox, coyote, other into adults. Adult worms live in the lumen of the small intestine, where they attach to the intestinal carnivores, human), A. tubaeforme (cat) and Uncinaria stenocephala (cat, dog, fox). The wall with resultant blood loss by the host . Most adult worms are eliminated in one to two years, adult stage is small, 1-2 cm long, with the but the longevity may reach several years. Some A. duodenale larvae, following penetration of the females slightly larger, usually located in the host skin, can become dormant (in the intestine or muscle). In addition, infection by A. duodenale small intestine. They will produce eggs with may probably also occur by the oral and transmammary route. N. americanus, however, requires a clear, translucent shells, developing quickly in transpulmonary migration phase. a warm and moist environment to blastomeres Symptomatology and diagnosis Zoonotic transmission and human disease and within two (2) days to three (3) weeks – Adult dogs having chronic hookworm infection The growing popularity of dogs and cats depending on temperature and humidity – to may have no symptoms at all. Indications of in the United States as well as high rates of infective larvae (Table 1). the disease are weakness, listlessness, anemia hookworm infections have resulted in widespread Both puppies and kittens acquire hookworm (pale mucosae, gingiva), rough fur coat and contamination of the soil with eggs and infective infections through ingestion or skin penetration often, diarrhea with black/bloody feces. Another larvae. Epidemiologic studies have implicated by infective larvae or from infective larvae expression is eosinophilic enteritis produced the presence of dogs, particularly puppies, in a passed in utero or with their dam’s milk. by intestinal infection resulting in eosinophilia household, and pica (dirt eating) as the principal Hookworms suck large amounts of blood and abdominal pain. Live larvae can be found in risk factors for human disease. Children’s play from their hosts, and while infected animals feces of affected animals. Eggs in the feces can habits and their attraction to pets put them at may look healthy in the first weeks of life, be identified microscopically following standard higher risk for infection than adults, and their they can develop a rapidly severe, often fatal, flotation procedures over 33 percent zinc sulfate. symptoms are more severe. Humans can become anemia. Open intestinal infections can appear as However, there may be a lag of several weeks infected with hookworms through ingestion of early as 2 weeks (dogs) to 3 weeks (cats) of age, between infection and the deposition of eggs, so infective larvae or through direct penetration of leading to environmental contamination with that the absence of eggs does not imply absence the skin. When infective larvae penetrate the skin, infective larvae. of the disease. Egg counts are important to they undergo a prolonged migration that causes determine the effect of treatment. a condition known as cutaneous larva migrans. Table 1 A.caninum A.braziliense A.tubaeforme U.stenocephale Adult male (mm) 11-13 x 0.34-0.39 5-7.5 x 0.19-0.27 9.5-11 x 0.3-0.35 5 - 9 x 0.2 Adult female (mm) 14-20.5 x 0.50-0.56 6.5-10.6 x 0.22-0.32 12 – 15 x 0.38 – 0.43 7 – 13 x 0.2 – 0.25 Oval eggs(micron) 56 - 75 x 34 - 47 75 - 95 x 41 - 45 55 - 78 x 34 - 45 63 – 76 x 32 - 38 Teeth 6 + 2 4 6 Cutting plates Hosts Dog, fox, coyote, other Dog, cat, fox, other Felines Dog, cat, fox, other carnivores; humans carnivores; humans carnivores; humans Elite Page 1 larvae-contaminated soil include electricians, plumbers and other workers who crawl beneath raised buildings; sunbathers who recline on larvae-contaminated sand; and children who play in contaminated areas. While most hookworm infections are self-limiting, massive infections can lead to infection of deeper tissues. Outbreak in a Miami summer camp On July 19, 2006, the director of a children’s aquatic sports day camp notified the Miami- Dade County Health Department (MDCHD) of three campers who had received a diagnosis of cutaneous larva migrans (CLM), or “creeping eruption,” a skin condition typically caused by dog or cat hookworm larvae of the genus Ancylostoma. MDCHD conducted an investigation to determine the source and magnitude of the outbreak and prevent additional illness. Although CLM outbreaks are reported rarely to the Florida Department of Health, evidence indicates that CLM is a potential health hazard in Florida. This disease cluster highlights the importance of appropriate environmental hygiene practices and education in preventing CLM. Life cycle (Cutaneous larval migrans) The camp property, which is located in Miami, Cutaneous larval migrans (also known as creeping eruption) is a zoonotic infection with hookworm includes swimming pools and a main building, species that do not use humans as a definitive host, the most common beingA. braziliense and A. volleyball court, playground with a sandbox, caninum. The normal definitive hosts for these species are dogs and cats. The cycle in the definitive picnic area and beach for boating and swimming. host is very similar to the cycle for the human species. Eggs are passed in the stool , and under The camp consisted of four two-week sessions favorable conditions (moisture, warmth, shade), larvae hatch in 1 to 2 days. The released rhabditiform held from June 5-July 28, 2006, and was divided into two programs: a half-day session for children larvae grow in the feces and/or the soil , and after five to 10 days (and two molts) they become aged 2-6 years, and a full-day session for children filariform (third-stage) larvae that are infective . These infective larvae can survive three to four aged 5-15 years. Approximately 300 campers and weeks in favorable environmental conditions. On contact with the animal host , the larvae penetrate 80 staff members attended each session. the skin and are carried through the blood vessels to the heart and then to the lungs. They penetrate into the pulmonary alveoli, ascend the bronchial tree to the pharynx and are swallowed. The larvae On July 20, camp administrators announced reach the small intestine, where they reside and mature into adults. Adult worms live in the lumen to all current campers, their parents and staff of the small intestine, where they attach to the intestinal wall. Some larvae become arrested in the members that three children had received tissues, and serve as a source of infection for pups via transmammary (and possibly transplacental) CLM diagnoses. Parents were asked to look routes . Humans may also become infected when filariform larvae penetrate the skin . With for various symptoms of infection, including most species, the larvae cannot mature further in the human host, and migrate aimlessly within the a snake-shaped (serpiginous) red rash, itching epidermis, sometimes as much as several centimeters a day. Some larvae may persist in deeper tissue and pus-containing lesions. In addition, camp after finishing their skin migration. administrators provided information about CLM to the households of any other campers and These larval migrations are characterized by the parts of the U.S, Central and South America). By staff members who attended sessions during the appearance of progressive, intensely pruritic, contrast, U. stenocephala is found in northern summer. MDCHD advised that persons with linear eruptive lesions, which are usually more climates (Canada, the northern U.S. and Europe). signs or symptoms seek medical care and contact extensive with A. braziliense infections. A. Both N. americanus and A. duodenale are found the health department to make a report. caninum larvae may also penetrate into deeper in Africa, Asia and the Americas. N. americanus tissues and induce symptoms of visceral larva MDCHD received 22 reports of persons (four predominates in the Americas and Australia, migrans, or migrate to the intestine and induce staff members and 18 campers, including the while only A.