''Neospora'' is a single celled

parasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...

livestock Livestock are the domesticated animals raised in an agricultural setting to provide labor and produce diversified products for consumption such as meat, eggs, milk, fur, leather, and wool. The term is sometimes used to refer solely to animal ...

and

companion animal A pet, or companion animal, is an animal kept primarily for a person's company or entertainment rather than as a working animal, livestock, or a laboratory animal. Popular pets are often considered to have attractive appearances, intelligence, ...

s. It was not discovered until 1984 in

Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and the ...

, where it was found in

dog The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the wolf. Also called the domestic dog, it is derived from the extinct Pleistocene wolf, and the modern wolf is the dog's nearest living relative. Do ...

s. Neosporosis, the disease that affects

cattle Cattle (''Bos taurus'') are large, domesticated, cloven-hooved, herbivores. They are a prominent modern member of the subfamily Bovinae and the most widespread species of the genus ''Bos''. Adult females are referred to as cows and adult ma ...

and companion animals, has a worldwide distribution. ''Neosporosis'' causes abortions in cattle and paralysis in companion animals. It is highly transmissible and some herds can have up to a 90%

prevalence In epidemiology, prevalence is the proportion of a particular population found to be affected by a medical condition (typically a disease or a risk factor such as smoking or seatbelt use) at a specific time. It is derived by comparing the number o ...

. Up to 33% of pregnancies can result in aborted

fetus A fetus or foetus (; plural fetuses, feti, foetuses, or foeti) is the unborn offspring that develops from an animal embryo. Following embryonic development the fetal stage of development takes place. In human prenatal development, fetal dev ...

es on one

dairy farm Dairy farming is a class of agriculture for long-term production of milk, which is processed (either on the farm or at a dairy plant, either of which may be called a dairy) for eventual sale of a dairy product. Dairy farming has a history th ...

. In many countries this organism is the main cause of abortion in cattle. Neosporosis is now considered as a major cause of abortion in cattle worldwide. Many reliable diagnostic tests are commercially available. ''Neospora caninum'' does not appear to be infectious to humans. In dogs, ''Neospora caninum'' can cause neurological signs, especially in congenitally infected puppies, where it can form cysts in the central nervous system.

Genome

The genome of ''Neospora caninum'' has been sequenced.Khan A, Fujita AW, Randle N, Regidor-Cerrillo J, Shaik JS, Shen K, Oler AJ4, Quinones M4, Latham SM5, Akanmori BD, Cleaveland S, Innes EA, Ryan U, Šlapeta J, Schares G, Ortega-Mora LM, Dubey JP, Wastling JM, Grigg ME (2019) Global selective sweep of a highly inbred genome of the cattle parasite ''Neospora caninum''. Proc Natl Acad Sci USA The results suggest a European origin for this parasite.

Effects of disease

Neospora caninum ''Neospora caninum'' is a coccidian parasite that was identified as a species in 1988. Prior to this, it was misclassified as ''Toxoplasma gondii'' due to structural similarities. The genome sequence of ''Neospora caninum'' has been determined by ...

'' is a major pathogen of

and

s that occasionally causes clinical infections in horses, goats, sheep, and deer as well. The domestic dog is the only known definitive host for ''N. caninum''. In cattle, ''N. caninum'' is a major cause of bovine abortion in many countries and is one of the most efficiently transmitted parasites with up to 90% of some bovine herds infected. ''N. caninum'' causes abortion in both beef and dairy cattle. Another important factor is the gestational age and hence immunocompetence of the fetus at the time of infection.Innes E, Wright S, Bartley P (2005) The host-parasite relationship in bovine neosporosis. Vet Immunopathology. 108:29-36 Early in gestation, ''N. caninum'' infection of the

placenta The placenta is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate mate ...

and subsequently the fetus usually proves fatal, whereas infection occurring in mid to late

pregnancy Pregnancy is the time during which one or more offspring develops (gestation, gestates) inside a woman, woman's uterus (womb). A multiple birth, multiple pregnancy involves more than one offspring, such as with twins. Pregnancy usually occur ...

may result in the birth of a congenitally infected but otherwise healthy calf. Recent studies have broadened the list of known intermediate hosts to include birds. ''N. caninum'' has recently been found to infect domestic

chicken The chicken (''Gallus gallus domesticus'') is a domesticated junglefowl species, with attributes of wild species such as the grey and the Ceylon junglefowl that are originally from Southeastern Asia. Rooster or cock is a term for an adu ...

s and house sparrows (''

Passer domesticus The house sparrow (''Passer domesticus'') is a bird of the sparrow family Passeridae, found in most parts of the world. It is a small bird that has a typical length of and a mass of . Females and young birds are coloured pale brown and grey, an ...

'') which may become infected after ingesting parasite oocysts from the soil. Darwich, L;Cabezón O, Echeverria I, Pabón M, Marco I, Molina-López R, Alarcia-Alejos O, López-Gatius F, Lavín S, Almería S (2012) Presence of ''Toxoplasma gondii'' and ''Neospora caninum'' DNA in the brain of wild birds. Veterinary Parasitology 183: 377–381 The presence of birds in cattle pastures has been correlated to higher infection rates in cattle.Mineo T, Carrasco A, Raso T, Werther K, Pinto A, Machado R (2011) Survey for natural ''Neospora caninum'' infection in wild and captive birds. Veterinary Parasitology 182: 352–355. Birds may be an important link in the transmission of ''N. caninum'' to other animals.

Epidemiology

The life cycle is similar to ''

Toxoplasma ''Toxoplasma gondii'' () is an obligate intracellular parasitic protozoan (specifically an apicomplexan) that causes toxoplasmosis. Found worldwide, ''T. gondii'' is capable of infecting virtually all warm-blooded animals, but felids, such as d ...

''. An infected dog will pass the

oocysts Apicomplexans, a group of intracellular parasites, have life cycle stages that allow them to survive the wide variety of environments they are exposed to during their complex life cycle. Each stage in the life cycle of an apicomplexan organism i ...

through its feces and infect food or

water Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...

. A cow or other animal will then up take the parasite. The parasite will undergo asexual reproduction in the animal's muscle until it is eaten by a dog. There,

sexual reproduction Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete ( haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote th ...

will occur and oocysts will be created and passed through the feces. Dogs are often the

definitive host In biology and medicine, a host is a larger organism that harbours a smaller organism; whether a parasitic, a mutualistic, or a commensalist ''guest'' ( symbiont). The guest is typically provided with nourishment and shelter. Examples include ...

but can act as an intermediate host as well. Cows are usually the intermediate host. No horizontal cow-to-cow transmission have been shown, although salival interactions have been suggested. Vertical transmission can occur when an infected cow gives birth to an infected

calf Calf most often refers to: * Calf (animal), the young of domestic cattle. * Calf (leg), in humans (and other primates), the back portion of the lower leg Calf or calves may also refer to: Biology and animal byproducts * Veal, meat from calves * ...

—the calf survives the infection and grows into an adult. Vertical route is the major route of transmission in cattle and is extremely efficient as the rate of transmission is usually between 80 and 100%. A heifer calf that is born congenitally infected is capable of transmitting the infection to the next generation when she becomes pregnant, thus maintaining the infection in the herd. Transplacental transmission in cattle is considered the major route of transmission. The life cycle is typified by three infectious stages: tachyzoites, tissue cysts, and oocysts Tachyzoites and tissue cysts are the stages found in the intermediate hosts, and they occur intracellularly.

Detection of disease

Detection: the presence of cerebral and cardiac lesions can be seen on aborted bovine fetuses originating from a single farm. The parasite is identified in the tissues of many bovine aborted fetuses but also of stillborn calves and, rarely, of clinically affected newborn calves. The diagnosis of the infection is assisted through histopathology and immunohistochemical examination of aborted fetuses and serologic testing of cattle for evidence of infection. The abortion is the only clinical sign and can occur from the third month of pregnancy and onwards. Most of the abortions take place between the 5th and 6th months of pregnancy Losson, B. 2006. "Neosporosis in Cattle". World Buiattrics Congress. http://www.ivis.org/proceedings/wbc/wbc2006/losson.pdf?LA=1 The fetus is either resorbed, autolyzed, mummified, stillborn, born alive with clinical signs, or born clinically normal but chronically infected. At calving, infected calves may be clinically normal or may have neurologic signs, be underweight or unable to stand.

Prevention and control

Embryo transfer is recommended as a method of reproduction to reduce the chances of contracting the disease, as long as the disease status of the donor cow is checked. It is not recommended to rebreed heifers or cows that have this disease. Seropositive animals should be culled. To prevent horizontal transmission it is important to prevent the contamination of feed and water via the shedding of oocysts by dogs and possibly other canids like the fox. These animals should not have access to animal premises although this might be difficult to achieve. There are no drugs or vaccines available yet to prevent or control the disease.

References

External links

* Apicomplexa genera Conoidasida Parasites of dogs Parasites of mammals {{Apicomplexa-stub