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There are more than 2,000 species of tiny (0.04 to 0.15 inches), wingless, blood-sucking fleas that live on the body of the host they infest. Although fleas cannot fly, they have developed ...
It causes a disease commonly referred to as white spot disease due to the macroscopically visible trophonts (up to 1 mm in diameter) in the skin and fins. The trophont, continuously rotating, is surrounded by host cells (epidermal cells and leukocytes ), producing a minute elevation of the skin.
The human flea (Pulex irritans) – once also called the house flea [1] – is a cosmopolitan flea species that has, in spite of the common name, a wide host spectrum. It is one of six species in the genus Pulex ; the other five are all confined to the Nearctic and Neotropical realms . [ 2 ]
Gongylonema pulchrum is the only parasite of the genus Gongylonema capable of infecting humans. Gongylonema pulchrum infections are due to humans acting as accidental hosts for the parasite. There are seven genera of spirudia nematodes that infect human hosts accidentally: Gnathostoma, Thelazia, Gongylonema, Physaloptera, Spirocerca, Rictularia.
The disease was spread to humans by rodents, such as the black rat, which were bitten by infected fleas. Major outbreaks included the Plague of Justinian , about 540, and the Black Death , about 1350, each of which killed a sizeable fraction of the world's people.
By stage 2 (days 1–2), penetration is complete and the flea has burrowed most of its body into the skin. Only the anus, the copulatory organs, and four rear air holes in fleas called stigmata remain on the outside of the epidermis. The anus will excrete feces that is thought to attract male fleas for mating, described in a later section.
Common symptoms of food poisoning include stomach aches and pain, nausea, fever, vomiting, diarrhea and headache. "Those most at risk for severe foodborne illness include children under 5 ...
However, the disease can also develop without the fish showing any external signs of illness, the fish maintain a normal appetite, and then they suddenly die. The disease can progress slowly throughout an infected farm and, in the worst cases, death rates may approach 100 per cent. It is also a threat to the dwindling stocks of wild salmon.