Oviparous ( lay eggs) Laying unsegmented eggs Trichuris trichiuria Laying eggs with segmented ova Laying eggs containg larva Enterobuis vermicularis • Viviparous (nematodes which give birth to larvae) • medinesis • • •

• Ovo-viviparous (laying eggs containing larvae) • Stongyloides stercoalis Adult worm habitat Human Nematodes

Phylum: Nematoda Class: Secernentea Family: Onchocercidae Genus: Wuchereria Brugia Loa Family: Dracunulidae Genus: Dracunculus • These nematodes are known as filariae and consist of a group of nematodes which have successfully invaded the blood stream (Lymphatic system) , connective tissue or serous cavities of .

• Sexually mature female worms release microfilaria, which are pre-larval stages. These are released into the bloodstream. Most species are known to be Ovi-viviparous and some have ‘sheathed’ microfilaria. Filariae are Blood Nematodes

• Wuchereria bancrofti: The causative agent of Bancroftian Filariasis • Brugia malayi: The causative agent of Brugian of humans • : A human filarial parasite from Indonesia • : A cutaneous filarial parasite of humans • : The Causative agent of River Blindness microflariae Differential characters of microflariae Lymphatic filariasis • Lymphatic filariasis is a caused by threadlike worms () living in the human lymphatic system mainly adults

• There are three known species of the filarial nematode that can cause lymphatic filariasis: Wuchereria bancrofti, Brugia malayi and Brugia timori. Elephantaisis Lymphedema

In men: swelling of the scrotum (hydrocele) W. bancrofti

Distribution

• W. bancrofti is distributed throughout the tropical regions of Asia, Africa, China, the Pacific and isolated locations in the Americas. Current estimates (WHO, 1994) suggest that 100 million people are infected with lymphatic filariae of all types, and most of these cases are bancroftian filariasis. • Nocturnally periodic forms occur indigenously in almost every tropical and subtropical country and are very widespread. However they show focal and periodic distribution patterns which are dependent on their vector of transmission. Culcicine or anopheline mosquitoes are the main vectors of the nocturnally periodic forms of W. bancrofti, while day biting Aedes polynesiensis transmit the subperiodic form in various pacific islands. Microflaria bancrofti Microfilariae W. bancrofti B. malayi

Sheathed , body curved Have nuclei extend to the tip of and No nuclei in the tail the tail Mosquito vector : Culex quinquefasciatus Life Cycle

• The third-stage infective larvae (L3) enter the blood through the wound made by the mosquito. They then migrate to the nearest lymph gland where they mature into the thread like adult worms about 3 months to 1 year later. The average incubation time before patency is about 15 months. The mature adults can survive for 5 to 10 years and the damage of the lymphatic vessels they cause and the immune system's response to their presence (and that of microfilaria and newly innoculated L3). Pathology

• Following infection with third stage larvae there is usually a period of vigorous immune response to the invading larvae. If the larvae are not cleared from the body during this period then the various pathologies associated with filarial infection can develop. Most of these conditions do not appear to arise from the effects of the nematodes themselves but from immune reactions to their presence. The most pronounced of these is the damage to the lymphatic vessels which is mediated by the immune system's response to the adult worms living in them. These immune responses (Lymphangitis) are characterized by inflammation of the affected area (which are usually extremities) and fever. Repeated episodes of lymphangitis lead to the formation of fibrous and calcified tissues (as seen in the X-ray below, picture taken from Peters and Gilles 1991) in and around the lymphatic vessels. • With W. bancrofti infections these enlargements are usually unilateral and the incapacitating deformities often require radical surgery to remove the surplus fibrous and calcified tissues. The microfilariae in the blood and lungs can also cause an IgE mediated allergic response which results in asthma like symptoms. This condition is called tropical eosinophilia and is treatable with macro and microfilaricides • There are two strains of W. bancrofti; • 1. The nocturnal periodic strain which is widely distributed in endemic regions (i.e. Africa, India and the Far East and also parts of China, Korea and Japan) with the microfilariae being in their highest concentrations between the hours of 10pm and 2am. • 2. The sub-periodic (non periodic) strain which is found in the Pacific region, and has a microfilaremia all the time with the highest numbers being detected between noon and 8pm. Distribution of Brugia malayi

• The endemic range of Brugia malayi is confined to South and South-East Asia from India in the west to Korea in the east. LikeW. bancrofti its distribution is dependent on its mosquito vectors. The nocturnally periodic form is found in areas with rice fields and the nocturnally subperiodic form is found in rural villages and plantations along the lower reaches of major rivers in swamp forests (for some comments on periodicity). Partono has proposed the subdivision of B. malayi into zoophilic and anthropophilic strains. The former is transmissible to cats, monkeys, and laboratory gerbils • Although very similar in morphology, W. bancrofti, has no nuclei in the tail, • whereas B. malayi, center, and B. timori, not pictured, have nuclei that extend to the tip. Nuclei in the tip of the tail can be seen as swelled areas, highlighted by arrows in the right picture. Wuchereria bancrofti

• W. bancrofti is the most widespread cause of lymphatic filariasis. It is more common to find elephantiasis in patients affected with W. bancrofti than those affected with the Brugian filariasis, although it can occur. • Brugian filariasis also does not characteristically include symptoms associated with the genitalia or chyluria, while Bancroftian filariasis often expresses these symptoms in heavily infected patients. W. bancrofti

• The morphology of W. bancrofti is the most significant differentiation from other species. The microfilariae, or larval stage of W. bancrofti, are sheathed, and range from approximately 245 to 300 µm. It can take several months for the microfilariae to sexually mature, and in the adult stage they can live for several years. As adults, the males range from 2.5 to 4 cm, and the females range from 5 to 10 cm. As a roundworm, the shape of the W. bancrofti name matches its descriptive classification. One end of the round body is blunt, while the other is pointed. Nuclei do not appear at the end of the tail, which is a major difference from other microfilariae. Both Bancroftian and Brugian filariae lack a digestive system, instead absorbing nutrients from their hosts. Brugia malayi

• The distribution of B. malayi is very similar to that of W. bancrofti. However, cases are concentrated in Asia, including South China, India, Indonesia, Thailand, Vietnam, Malaysia, the Philippines, and South Korea. Other differences between B. malayi and W. bancrofti is the vector and reservoir. While W. bancrofti is transmitted mainly by culex, B. malayi is transmitted by Mansonia mosquitos. • Since these mosquitos feed primarily during the day, B. malayi microfilaria can be found in the blood during the day, while microfilaria of W. bancrofti is found at high levels at night. The time variation in microfilarial levels is known as periodicity. Additionally, W. bancrofti has no known reservoir, while B. malayi has been found in Macaques, leaf monkeys, cats and civet cats. In Indonesia, human cases have been transmitted from , which poses a particular challenge to the control of B. malayi. • Although most of the symptoms of Brugian filariasis are identical to Bancroftian filariasis, there are some differences in clinical presentation. First, Brugian filariasis tends to have a higher occurrence of ulcerated nodules, and as mentioned above, rarely involve genital swelling or chyluria. In addition, elephantiasis is experienced alomost explicitly in the lower part of the limbs (below the knee or below the elbow). Treatment and prevention, with the exceptional control problem associated with the animal reservoirs of Brugian filariasis, is the same as Bancroftian filariasis. • The morphology, like that of W. bancrofti, is the most reliable way to differentiate species type. Generally, microfilariae range from 200 to 275 µm. Adult size is not well-known, as very few have actually been found. Microfilariae of B. malayi are sheathed like W. bancrofti, and have a very similar shape. However, the nuclei extends nearly to the tip of the tail, a characteristic not shared with W. bancrofti. Loa loa: loasis • Loa loa, also known as the African eye worm, is a filarial nematode endemic in the rain forests of West and Central Africa. It is transmitted by Chrysops species, also known as mango flies or horse flies and humans are the only known reservoir. It is estimated that 2-13 million humans are infected with the larvae. • Adults migrate in the subcutaneous tissues of man and monkeys, with them eventually migrating across the eyeball under the conjunctiva. • The adult worms live in the subcutaneous and deep connective tissues and the microfilariae are found in the peripheral blood, where they can be in ingested by the Chrysops fly (day biting fly) The adults can live in the tissues for up to 17 years. • Once the microfilariae have been taken up by the Chrysops during a blood meal they develop within the fat body. They develop through to L3 within 10–12 days. The microfilariae, L3 re-enter the hosts blood stream when the fly takes another blood meal. They reach adult worms within 4- 6 months living in the subcutaneous and deep connective tissues. • The microfilariae exhibit diurnal periodicity, the highest numbers being detected in blood between 10am and 2pm.

Morphology • Adult males of Loa loa are 2–3.5cm long and the females from 5- 7cm. The microfilariae of Loa loa are 250-300µm. They possess a sheath which stains blue-grey with Delafield’s hematoxylin. The sheath does not stain with Giemsa. The tail gradually tapers to a rounded end, the densely packed nuclei extending to the tip.

Microfilariae: loa loa

The microfilariae are found in the peripheral blood, The microfilaria are kinked and sheathed. Nuclei crowded extending to tip of tail; tip of tail tapers. Loa Loa - The African Eye Worm

• Loa loa is a blood dwelling nematode that is parasitic in humans. The adult worm wanders through the subcutaneous tissue but is most obvious as it crosses the conjunctiva of the eye hence leading to its common name, the African eye worm. • Like all roundworms, Loa loa is sexual so a male and female worm must be present in the same host for a full infection to ensue. Upon reproduction the female worm produces sheathed eggs called microfilariae which circulate in the blood stream. • Loa loa is endemic to parts of Western Africa, especially in the rainforests of the Congo and Sudan. Symptoms are less serious in natives of these areas with complications occurring mostly in visitors and tourists. • Loiasis is caused by the filarial nematode Loa loa which is transmitted to humans by day- biting Chrysops flies Distribution • The microfilariae closely resemble the microfilariae of W. bancrofti however in stained films they assume a stiff angular attitude. The cuticle sheath also does not stain with Giemsa (see picture below taken from Peters and Gilles 1991). Larvae and pathology of loa loa Clinical disease

• Many patients infected with Loa loa appear to be asymptomatic and the migration of the adult worm through the subcutaneous tissues often goes unnoticed, unless passing beneath the conjunctiva of the eye. They can be seen crossing the eye, but it is a rapid process taking approximately 15–20 minutes. Hyperesinophilia and increased antibody levels, especially IgE are also noted. Eye-worm episodes are as equally common in man as well as women with common reoccurrences. There is an increased incidence with age. • The most common pathology associated with Loa loa infections are Calabar swellings, which are inflammatory swellings resulting in a localized subcutaneous edema. These swellings are due the host’s response to the worm or its metabolic products and can be found anywhere in the body but most commonly in the extremities. These swellings last from 1–3 days. They develop rapidly and last one to three days, usually accompanied by localized pain, urticaria and pruritis. There is a higher frequency of Calabar swellings in women with common reoccurrences. • Serious complications such as cardiomyopathy, encephalopathy, nephropathy and pleural effusion have been recorded. • .

• Introduction • Dracunculus medinensis is a non-filarial parasite as it only has one uterus whereas filaria have two. It is usually associated with places where there is a lack of clean drinking water e.g. step wells in India, covered cisterns in Iran, and ponds in Ghana. The life cycle usually involves copepod intermediate host. They are parasitic in the connective tissue or coelom of vertebrates. The disease associated with this parasite is known as . • Mature female worms which are gravid with microfilariae migrate to the superficial layers of skin of humans, especially those regions which are most likely to come in contact with water, such as the ankle, foot, arms and shoulders. Here the worms secrete a substance (substance is unknown) which causes a blister to rise over its anterior end where it has pierced the lower layers. The blister eventually forms into an ulcer which on contact with water, the uterus is projected out of the ulcer cavity, and a cloud of milky white secretion, containing hundred of active larvae, is released. Once out of the water again the uterus dries and shrivels preventing the release of further larvae. • If the microfilariae are ingested by an appropriate species of Cyclops, they break though the soft mid-intestine wall and come to lie in the body cavity. The larvae undergo two molts and become infective in approximately three weeks. Humans become infected by accidentally ingesting through drinking water the infective Cyclops. Upon ingestion the larvae are activated to penetrate through the gut wall, and migrate through the tissues, molting twice and finally becoming lodges in the viscera or subcutaneous tissues. Maturation of the worms is slow taking about one year to reach sexual maturity before the females are ready to migrate to the skin to release their larvae. Life cycle

Clinical Disease

• After ingestion of the Cyclops, there is no specific pathology associate with the mucosal penetration and larval maturation in the deep connective tissues. Erythema and tenderness can be associated with blister formation. The patient can also exhibit vomiting, diarrhea, asthmatic attacks. Symptoms usually subside when the lesion erupts. If the worm is removed, healing usually occurs without any problems. If the worm is damaged or broken during removal, there may be intense inflammatory reaction with possible cellulitis along the worms migratory tract. This can result in arthritis and synovitis. • The best remedy for removing the adult worm is a slow process of daily gently rolling the worm around a small stick and slowly pulling it out of the skin. With this method you must be careful not to pull apart the worm as it will recoil back into the skin and cause secondary infections. • This parasite is currently being approached with a strict control program. The program includes stopping people from drinking infected water, putting muslin over water collection jars, educating the communities about the parasite, and adding temphos to the water to kill it off.