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Contracaecum is a genus of parasitic nematodes from the family Anisakidae. These nematodes are parasites of warm-blooded, fish eating animals, i.e. mammals and birds, as sexually mature adults. The eggs and the successive stages of their larvae use invertebrates and increasing size classes of fishes as intermediate hosts.
The eggs measure 50 to 60 μm by 20 to 30 μm, and have a thick shell flattened on one side. [18] The small size and colourlessness of the eggs make them invisible to the naked eye, except in barely visible clumps of thousands of eggs. Eggs may contain a developing embryo or a fully developed pinworm larva. [18] The larvae grow to 140–150 μm ...
Fertile egg as can be seen in a microscope Fertile egg in human faeces (detail) Infertile egg. Ascaris lumbricoides is characterized by its great size. Males are 2–4 mm (0.08–0.2 in) in diameter and 15–31 cm (5.9–12 in) long. The male's posterior end is curved ventrally and has a bluntly pointed tail.
The nematode infects fowl of all ages, but the greatest degree of damage is often found in birds under 12 weeks of age. Heavy infection is the major cause of weight depression and reduced egg production in poultry husbandry. In severe infections, intestinal blockage can occur and causing haemorrhagic enteritis.
A third method of diagnosis is examining a sample from under their fingernails under a microscope as itching around the anal area is common and therefore they may have collected some eggs under their nails as a result. [23] Pinworms do not lay eggs in the feces, [21] but sometimes eggs are deposited in the intestine. [19]
Nematode sperm is thought to be the only eukaryotic cell without the globular protein G-actin. [49] Eggs may be embryonated or unembryonated when passed by the female, meaning their fertilized eggs may not yet be developed. A few species are known to be ovoviviparous. The eggs are protected by an outer shell, secreted by the uterus.
Eggs of H. gallinarum are passed in feces by the host. At optimal temperature (22 °C), they become infective in 12–14 days and remain infective for years in soil. Upon ingestion by a host, the embryonated eggs hatch into second-stage juveniles in the gizzard or duodenum, and are passed to the cecum.
The release of oocytes (eggs) in female worms does not depend upon the presence of a male worm, although they may attract male worms using unidentified pheromones. [8] The first larval stage, microfilariae , are 300 μm in length and unsheathed, meaning that when they mature into microfilariae, they exit from the envelope of the egg.