Blood fluke
Blood flukes, belonging to the genus Schistosoma, are parasitic flatworms that primarily feed on the blood and plasma of their hosts, which include humans and some animals. They are responsible for schistosomiasis, a significant global health concern, ranking alongside malaria as one of the most prevalent diseases. There are over 20 species of blood flukes, with three main types affecting humans: Schistosoma haematobium, which targets the bladder and reproductive organs; Schistosoma mansoni, which affects the liver and intestines; and Schistosoma japonicum, which can also impact the brain.
Adult blood flukes are small, flat, oval-shaped organisms that attach to their host's organs using specialized appendages. They reproduce sexually within the human gut, where males and females live together. The eggs laid by the flukes can cause significant pain as they pass through human tissue. After being released into water, the eggs hatch into larvae that seek out intermediate hosts, typically snails, to continue their life cycle. Though blood flukes can live inside a human for several years, they face threats from environmental factors and medical interventions aimed at controlling their populations.
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Blood fluke
Like other parasitic flatworms, the blood fluke feeds on the fluids of its host. In the case of the blood fluke the fluids it feeds on are blood and plasma, and the hosts are humans. They can also live inside animals. Blood flukes cause the disease schistosomiasis, one of the two most common diseases in the world. The other is malaria.
Kingdom: Animalia
Phylum: Platyhelminthes
Class: Trematoda
Order: Diplostomida
Family: Schistomsomatidae
Genus: Schistosoma
Species: Various (see below)
Although there are over 20 species in the genus Schistosoma, there are three main types of blood flukes which affect humans. Schistosoma haematobium causes diseases of the bladder and reproductive organs. This blood fluke is generally found in Africa, particularly Egypt, and in the Middle East. Schistosoma mansoni causes diseases in the liver and intestines and is generally found in parts of Africa, the Middle East, Brazil, Venezuela, Surinam, and some of the Caribbean islands. The third kind of blood fluke is Schistosoma japonicum. It also affects the liver and intestines, but may also affect the brain. This blood fluke occurs in China, Japan, the Philippines, and parts of Southeast Asia.
Like other parasitic flatworms, the blood fluke is small, flat, and oval with hooks, claws, discs, and suckers on one end. The blood fluke uses these appendages to attach itself to the organs of its host. The blood fluke generally grows to be no more than one inch (2 1/2 centimeters) long and has a bilaterally symmetrical body with no definite head. Bilateral symmetry means that each side of its body is an exact mirror image of the other side. Like blood flukes, humans are also bilaterally symmetrical. If a human were to be split from top to bottom there would be two identical halves.
The blood fluke is one of the few parasitic flatworms which is not asexual, or able to reproduce individually. Male and female blood flukes live together within the veins of the human gut. The male blood fluke is fatter than his female companion and is able to keep her protected within the folds of his body wall. Male and female blood flukes mate within the human gut and deposit their eggs into the body of their host. These eggs are then released into water through human urine. This generally takes place in areas where there is little care for sanitation and humans frequently relieve themselves into lakes, ponds, and streams. Although the male and female adult blood flukes do little harm to their host, their eggs pass through human tissue to get outside of the host. This process is very painful for the humans.
Once the eggs are in the water the young blood flukes hatch into free-swimming miracidia larvae. During this larval stage the young blood flukes swim through the water searching for temporary hosts. These hosts are often snails. Once the larvae find appropriate hosts they dig into the creatures' bodies and begin developing into sporocysts and later into many cercariae larvae. These larvae then leave the bodies of the snails to find their permanent hosts, other humans. When people stick their hands or feet into waters infested with blood flukes, the tiny creatures break into the skin of the humans and make their way into the guts of their new hosts.
The blood fluke is threatened by the environment when outside its host and by the death of its host when living as a parasitic flatworm. It is also threatened by new medications and sanitary measures intended to rid humans of these dangerous guests.
The blood fluke generally lives inside a human host for three to four years, although they can live up to 40 years. While blood flukes are not a threatened species, they can live inside and threaten already endangered animals.
Bibliography
“Schistosomiasis.” World Health Organization (WHO), 1 Feb. 2023, www.who.int/news-room/fact-sheets/detail/schistosomiasis. Accessed 21 Mar. 2024.
“Schistosomiasis: Causes, Symptoms, Diagnosis & Treatment.” Cleveland Clinic, 23 Mar. 2022, my.clevelandclinic.org/health/diseases/22631-schistosomiasis. Accessed 21 Mar. 2024.