Generally, the host does not gain from this relationship and often suffers as a result. In many cases, the parasite changes the host physically or behaviorally; in extreme examples known as parasitoids the organism consumes, sterilizes or kills their host. Many parasites depend on human hosts to facilitate their life cycles — there are a huge number of organisms that exploit our bodies, some benign, some rather more unpleasant and harmful. Parasites have developed their lifestyles and evolved in tandem with their host species, resulting in life cycles that can be incredibly complex, fascinating, disturbing and often extremely bizarre.
The Blood Nematodes Many of them are of medical and veterinary importance attacking man and various domestic animals being transported by various vectors, including mosquitoes.
The nematodes from this order require intermediate hosts for the completion of their life cycle. The morphology of these nematodes consist of a cylindroid pharynx with an anterior muscular portion and a posterior glandular portion; the males have well-developed alae a flat, wing-like anatomic process or part and spirally coiled tails.
Sexually mature female worms release microfilaria, which are pre-larval stages. These are released into the bloodstream. The filarial nematodes which parasitize man consist of Wuchereria bancrofti, Brugia malayi, Brugia timori and Loa loa, Onchocerca volvulus, Mansonella perstans, Mansonella streptocerca and Dipetalonema streptocerca.
They inhabit a range of locations within the body; lymph glands, deep connective tissue, subcutaneous tissues or mesenteries. Invasions of these tissues usually result in inflammatory reactions which is a typical symptom of a human filarial infection.
In some cases these result in fleshy deformities known as elephantiasis. It has been estimated that approximately one billion people in tropical and subtropical countries are exposed to the risk of filarial infections and at least million are infected with filariasis.
The species which are primarily responsible for these human filarial infections are Wuchereria bancrofti, Brugia malayi and Onchocerca volvulus.
Wuchereria bancrofti Introduction Wuchereria bancrofti is a nematode causing lymphatic filariasis throughout the tropics and subtropics and is transmitted by the mosquito. There are two strains of W. The nocturnal periodic strain which is widely distributed in endemic regions i.
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. The sub-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.
Humans are the only known reservoir host of W. The adult worm occurs in tightly coiled nodular masses in the major lymphatic ducts. The main vector is Culex quinquefasciatus, a mosquito that is particularly common in towns and cities, breeding in organically polluted water, resting in houses and feeding by night on their human occupants.
Typical breeding sites include: In rural areas throughout Africa, Anopheles gambiae and Anopheles funestus are involved in transmission.
Elsewhere other anopheline mosquito species may transmit bancroftian filariasis in rural areas. In Papua New Guinea, Mansonia species may act as a vector. Life Cycle Microfilariae enter the host during a blood meal when the vector, a mosquito, punctures the skin.
The infective larvae enter through the wound and migrate to the peripheral lymphatics where they grow to mature male and female worms. They can live there for several years. After mating, the gravid females release sheathed microfilariae into the peripheral blood where they can be detected months after the initial infected bite.
The mosquito acquires the infection by ingestion of the microfilaria in the blood meal. The microfilariae lose their sheath on arrival in the stomach of the mosquito due to gastric juices. The larvae migrate to the thoracic muscles and develop into infective larvae over a period of days.
The larvae then migrate to the mouthparts of the mosquito which infects the host during a blood meal. The blood stages of filariae, microfilariae, vary in the times when they are present in the peripheral blood, corresponding with the peak biting time of the vector.
Thus, in nocturnally periodic forms the microfilaria are present in the peripheral blood circulation at night; during the day they reside in the deep tissues, particularly the lungs. Diagram showing the life cycle of Wuchereria bancrofti, the filarial nematode known to cause the disfiguring disease, elephantiasis, in man.
The male measures between 2. The microfilariae are mm in length. The tail of the microfilariae of W. The sheath the microfilariae of W. Microfilaria of Wuchereria bancrofti.True elephantiasis is the result of a parasitic infection caused by three specific kinds of round worms. The long, threadlike worms block the body's lymphatic system—a network of channels, lymph nodes, and organs that helps maintain proper fluid levels in the body .
Malaria is one of the most prevalent and serious infectious disease problems throughout the tropical and subtropical areas of the world. The disease infects more than million inhabitants of more than countries throughout Africa, Latin America, South America, Asia, and Oceana.
1 There are at least 1 million deaths annually due to malaria, primarily in children. Lymphatic filariasis, commonly known as elephantiasis, is a neglected tropical disease. Infection occurs when filarial parasites are transmitted to humans through mosquitoes.
Infection is usually acquired in childhood causing hidden damage to the lymphatic system. The painful and profoundly. It's bad enough looking at slimy creepy crawlies outside around us which give us chills down our spines and send us screaming for cover.
They look evil and slimy and they can do terrible things to us. Giardia. Giardia duodenalis (or Giardia intestinalis, Giardia lamblia) is one of the most common protozoan parasites of humans and mammals..
Giardia intestinalis. AJC1. You’re usually infected. Parasitic worms transferred to people by infected mosquitoes can block the lymphatic system, causing the puffiness and swelling of lymphatic filariasis (elephantiasis). Lymphatic filiariasis Worm larvae that make their way into lymph vessels can mature into adult worms.