Hymenolepiasis is infestation by one of two species of tapeworm: Hymenolepis nana or H. diminuta. Alternative names are dwarf tapeworm infection and rat tapeworm infection. The disease is a type of helminthiasis which is classified as a neglected tropical disease. Symptoms and signs Hymenolepiasis does not always have symptoms, but they usually are described as abdominal pain, loss of appetite, itching around the anus, irritability, and diarrhea. However, in one study of 25 patients conducted in Peru, successful treatment of the infection made no significant difference to symptoms. Some authorities report that heavily infected cases are more likely to be symptomatic. Symptoms in humans are due to allergic responses or systematic toxaemia caused by waste products of the tapeworm. Light infections are usually symptomless, whereas infection with more than 2000 worms can cause enteritis, abdominal pain, diarrhea, loss of appetite, restlessness, irritability, restless sleep, and anal and nasal pruritus. Rare symptoms include increased appetite, vomiting, nausea, bloody diarrhea, hives, extremity pain, headache, dizziness, and behavioral disturbances. Occasionally, epileptic seizures occur in infected children. Examination of the stool for eggs and parasites confirms the diagnosis. The eggs and proglottids of H. nana are smaller than H. diminuta. Proglottids of both are relatively wide and have three testes. Identifying the parasites to the species level is often unnecessary from a medical perspective, as the treatment is the same for both. Complications Abdominal discomfort and, in case of prolonged diarrhea, dehydration are possible complications. In 2015 an unusual complication was noted in a man whose immune system had been compromised by HIV. He developed multiple tumors of malignant cell nests within his body that had originated from a tapeworm in his intestines. Causes Hymenolepis worms live in the intestines of rats and are common in warm climates, and are generally found in the feces of rats, which are consumed by their secondary hosts—beetles. The worms mature into a life form referred to as a "cysticercoid" in the insect; in H. nana, the insect is always a beetle. Humans and other animals become infected when they intentionally or unintentionally eat material contaminated by insects. In an infected person, it is possible for the worm's entire lifecycle to be completed in the bowel, so infection can persist for years if left untreated. H. nana infections are much more common than H. diminuta infections in humans because, in addition to being spread by insects, the disease