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Home , Mansonella perstans, Visceral larva migrans

Tissue and Blood Dwelling

MLS 602: General and Medical Microbiology Lecture: 11 Edwina Razak [email protected] Learning Outcomes

• Describe the tissue of medical importance. • Evaluate different characteristics of tissue nematodes. • Explain and evaluate the different lifecycles of common intestinal nematodes of humans. • Critically analyse the parasitology methods used to diagnose intestinal nematodes. Introduction

• The Neglected Tropical Diseases (NTDs), which have suffered from a lack of attention by the public health community, include parasitic diseases such as lymphatic ,, STHs and Guinea worm disease. • The NTDs affect more than 1 billion people—one-sixth of the world’s population—largely in rural areas of low-income countries. These diseases extract a large toll on endemic populations, including lost ability to attend school or work, retardation of growth in children, impairment of cognitive skills and development in young children, and the serious economic burden placed on entire countries. Common Tissue Nematodes are:

• -adults in small intestines and larvae in tissues (mainly in muscles). • - (dog roundworms) larvae in organs (, brain, eyes) causing visceral migrans. • - (guinea worm) adult female in subcutaneous tissues. • Filarial worms Trichinella spiralis –

• most commonly associated with pork. • Trichinella spiralis is a parasite of carnivorous mammals. • common in rats and in swine fed uncooked garbage and slaughterhouse scraps. • result of consumption of raw or undercooked pork. Morphology

• Adult female worm measures 3-4 mm in length. • adult male worm measures 1.4-2.6 mm in length. • encysted larvae measure 800-1300 μm in length. Life cycle:

• Infective stage larvae are ingested in meat products. • Tissue is digested, larvae are freed in the intestine. • They mature into adult males and females. • Female in mucosa releases larvae. These disseminate throughout the body via the bloodstream. • Larvae encyst in striated muscle Life cycle: Pathology and Clinical features

There are three clinical phases: 1. The intestinal phase: lasting 1-7 days - asymptomatic; sometimes cause nausea, vomiting, diarrhea, constipation, pain , muscle pain, bilateral periorbital edema, and increased count.

2. Migrational phase - high fever, blurred vision, edema, and pleural pains.

3. The muscle phase: which causes myalgia, palpabral edema, , fever, , meningitis, bronchopneumonia. Laboratory Diagnosis

• Muscle Biopsy • Detection of larvae in blood or CSF • Detection of larvae and adult worms in stool (rare). • ELISA- Enzyme Linked Immunosorbent Assay Treatment: Thiabendazol Dracunculus medinensis – The Guinea Worm

• An important parasite in the Middle East, central India and Pakistan. Also found in Africa in the Sudan and scattered through central equatorial regions, and on its west coast. • It is believed to have been the ‘fiery serpent’ in the Bible, which tormented the Israelites on the banks of the Red Sea. The technique of extracting the worm by twisting it on a stick, still practised by patients in endemic areas is said to have been devised by Moses. • Sometimes classified with the filarial worms, but Dracunculus is not a true filaria. Worm oozing out from the ruptured blister Life Cycle

• Infective stage exists in a water flea (copepod – the intermediate ). • Humans become infected by drinking water containing the infected copepod. • Larvae penetrate the digestive tract to enter the deep connective tissues where they mature in about 1 year. • Females migrate to the subcutaneous tissue (usually the skin of the extremities). • Females release larvae which leave the human through ruptured blisters on the skin. • The larvae enter the water and are ingested by copepods.

Symptoms and Diagnosis

Major pathology and symptoms Diagnosis • Mild allergic symptoms such as • Visual observation of skin blister. urticaria during the migration The worm’s serpentine presence phase. beneath skin can be seen. • A papule develops into a blister • Induce release of larvae from the with localized erythrema and skin ulcer by applying cold water. tenderness. • Microscopy can identify the special • Generalized symptoms include features of the worm. nausea, vomiting, diarrhea, and • An intradermal test with guinea possibly asthma attacks. worm antigen elicits positive • Additional complications include response. secondary bacterial , permanent damage to joints. Filarial Worms

• The Filariae are long thread-like nematodes. Eight species inhabit portions of the human subcutaneous tissues and lymphatic system. • Adults of all species are parasites of vertebrate hosts. • Female worms produce eggs. The eggs modify, becoming elongated and worm- like in appearance and adapting to life within the vascular system. • Modified eggs, referred to as microfilariae, are capable of living a long time in the vertebrate host, but cannot develop further until ingested by an intermediate host and , an insect. • Microfilariae transform into infective larvae in the insect and are deposited in the next host when the insect takes a blood meal.

• Bancroft's Filariasis.” A blood & lymphatic dweller () . The often results in elephantiasis. • Vectors - Culex, Aedes, & Anopheles mosquitoes. • Diagnosis - Detection and identification of in stained blood smears. Exhibits a marked circadian migration, best seen at night after 10 P.M. • Morphology - Microfilariae are sheathed, and the nuclear column does not extend to tip of tail. General life cycle

• Human infection is acquired when infective larvae enter the skin at the ’s feeding site. • Larval migration and development takes place in tissue. • Adults are in various tissues (according to species). They mature and produce microfilariae.

Symptoms

• Swelling, due to allergic reaction • Accumulation of fluid occurs due to occurring around adult worms, produces obstruction of lymph vessels of the obstruction & elephantiasis. Each spermatic cord and also by exudation individual reacts differently. Very few from the inflamed testes and epididymis develop elephantiasis, but in some this is extensive • Filariasis does not kill, but may cause great suffering, disfiguration and disability • Associated with malaise, , nausea, vomiting and low grade fever Recurrent attacks of pruritus and urticaria may occur. Some develop ‘fugitive swellings’—raised, painless, tender, diffuse, red areas on the skin, commonly seen on the limbs. Laboratory Diagnosis

• Demonstration of microfilaria in peripheral blood. Microfilaria may also be detected in other specimens such as chylous urine or hydrocoele fluid. Sometimes it can be seen in biopsy specimens. • Microfilaria can be demonstrated in unstained as well as stained preparations. • Leishman stain is used for thin smears • A drop of blood on a slide with cover slip using EDTA specimen for immediate observation of worms. Other Filarial Worms

Brugia malayi • “Malayan filariasis.” A blood & lymphatic • The “blinding filaria.” Infections involve dweller. The infection can cause the dermis and subcutaneous tissues, elephantiasis, but is not as disfiguring or where adults gather within nodules. common as with Wuchereria bancrofti. • Vector - Simulium (blackfly, or buffalo • Vectors - Mansonia, Anopheles & Aedes gnat). mosquitoes. • Diagnosis - microfilariae are found in skin • Diagnosis - Detection and identification of scrapings from around nodules. microfilaria in stained blood smears. • Morphology - Microfilariae not sheathed; • Morphology - Microfilariae are sheathed, found only in skin, not in the blood nuclear column extends to tip of tail with stream. two nuclei near end of tail, one in a swelling just short of tail’s end, the other • The specimen is best collected around in the end of the tail. midday. Loaloa

• The “eyeworm.” Infections • Infections cause a localized involve the dermis and subcutaneous edema, subcutaneous tissues (Calabar particularly around the eye, swellings). because of larval migration and • Vector - Crysops (mango ), a death in capillaries. Living adults large fly with biting mouthparts. cause no inflammation; dying adults induce granulomatous • Diagnosis - Usually made from reactions. clinical symptoms, but if laboratory confirmation is • sheathed, nuclei extending to required,circardian migration pointed tail tip Loaloa - SEROUS CAVITY FILARIASIS . New World filaria seen only in Central and • Distributed in tropical Africa and coastal and the West Indies. South America. . The adult worms are found in the peritoneal • The adult worms live in the body cavities of and pleural cavities of humans. humans, mainly in peritoneum, less often in . The non-periodic unsheathed microfilariae pleura and rarely in pericardium. are found in the blood. • The microfilariae are unsheathed and . species are the vectors. Infection subperiodic. does not cause any illness. • Vectors are Culicoides species. African primates have been reported to act as . Diagnosis is made by demonstrating reservoir hosts. microfilariae in blood. No treatment is available. • Infection is generally asymptomatic, though it has been claimed that it causes transient abdominal pain, rashes and malaise. • Diagnosis is by demonstration of the microfilariae in peripheral blood. Features differentiating different species of Microfilariae LARVA MIGRANS

There are three types of larva Clinical features: migrans: • Majority are asymptomatic. • (Creeping • Eosinophilia eruption) • Cerebral, myocardial and 1. Ancylostoma braziliens: infects pulmonary involvement may cause both dogs and cats. death. 2. : infects only Diagnosis - Identification of larvae in dogs. tissue. • Treatment - Thiabendazole: 25 1. Toxocara canis (Dog ascarid) mg/kg twice daily for 5 days. 2. Toxocara catis Questions??

1. Type of sample required Wucheria bancrofti identification. 2. Lymphatic filariasis symptoms. 3. Name the three clinical phases for Trichenella.