''Baylisascaris'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of roundworms that infect more than fifty animal

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

Life cycle

''Baylisascaris'' eggs are passed in

feces Feces (also known as faeces American and British English spelling differences#ae and oe, or fæces; : faex) are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the ...

and become active within a month. They can remain viable in the environment for years, withstanding heat and cold. Animals become infested either by swallowing the eggs or eating another animal infested with ''Baylisascaris.''

Disease progression

After an animal swallows the eggs, the microscopic

larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...

e hatch in the

intestine The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The tract is the largest of the body's systems, after the cardiovascular system. T ...

and invade the intestinal wall. If they are in their

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 ...

they develop for several weeks, then enter the intestinal lumen, mature, mate, and produce eggs, which are carried out in the fecal stream. If the larvae are in a paratenic host, they break into the bloodstream and enter various organs, particularly the central nervous system. A great deal of damage occurs wherever the larva try to make a home. In response to the attack, the body attempts to destroy it by walling it off or killing it. The larva moves rapidly to escape, seeking out the liver, eyes, spinal cord or brain. Occasionally they can be found in the heart, lungs, and other organs. Eventually the larva dies and is reabsorbed by the body. In very small species such as mice, it might take only one or two larvae in the brain to be fatal. If the larva does not cause significant damage in vital organs, then the victim will show no signs of disease. On the other hand, if it causes behavioral changes by destroying parts of the brain, the host becomes easier prey, bringing the larva into the intestine of a new host.

Clinical signs in humans

Are the following: * Skin irritations from larvae migrating within the skin. * Respiratory discomfort, liver enlargement, and fever due to reaction to larvae migration. * Eye and brain tissue damage due to the random migration of the larvae. * Nausea, a lethargic feeling, incoordination and loss of eyesight. * Severe neurological signs including imbalance, circling and abnormal behavior, caused by extensive tissue damage due to larval migration through the brain, eventually seizures and coma.

Treatment

While deworming can rid the intestine of adult ''Baylisascaris'', no treatment has been shown to alleviate illness caused by migrating larvae. Despite lack of larvicidal effects,

albendazole Albendazole is a broad-spectrum antihelmintic and antiprotozoal agent of the benzimidazole type. It is used for the treatment of a variety of intestinal parasite infections, including ascariasis, pinworm infection, hookworm infection, trichuri ...

(20–40 mg/kg/d for 1–4 weeks) has been used to treat many cases.

''Baylisascaris'' species

Each ''Baylisascaris'' species has a host species that it uses to reproduce. The eggs appear in the host species' feces. They can then be ingested by, and infest, a variety of other animals (including humans) that serve as paratenic hosts. ''Baylisascaris'' species include: * ''

Baylisascaris procyonis ''Baylisascaris'' is a genus of nematode, roundworms that infect more than fifty animal species. Life cycle ''Baylisascaris'' eggs are passed in feces and become active within a month. They can remain viable in the environment for years, withs ...

'' (of

raccoon The raccoon ( or , ''Procyon lotor''), sometimes called the North American, northern or common raccoon (also spelled racoon) to distinguish it from Procyonina, other species of raccoon, is a mammal native to North America. It is the largest ...

s) * ''Baylisascaris melis'' (of European badgers) * ''Baylisascaris transfuga'' (of

bear Bears are carnivoran mammals of the family (biology), family Ursidae (). They are classified as caniforms, or doglike carnivorans. Although only eight species of bears are extant, they are widespread, appearing in a wide variety of habitats ...

s) * ''Baylisascaris columnaris'' (of

skunk Skunks are mammals in the family Mephitidae. They are known for their ability to spray a liquid with a strong, unpleasant scent from their anal glands. Different species of skunk vary in appearance from black-and-white to brown, cream or gi ...

s and American badgers) * ''Baylisascaris devosi'' (of fishers and

marten A marten is a weasel-like mammal in the genus ''Martes'' within the subfamily Guloninae, in the family Mustelidae. They have bushy tails and large paws with partially retractile claws. The fur varies from yellowish to dark brown, depending on ...

s) * ''Baylisascaris laevis'' (of

marmot Marmots are large ground squirrels in the genus ''Marmota'', with 15 species living in Asia, Europe, and North America. These herbivores are active during the summer, when they can often be found in groups, but are not seen during the winter, w ...

s) * '' Baylisascaris schroederi'' (of

giant panda The giant panda (''Ailuropoda melanoleuca''), also known as the panda bear or simply panda, is a bear species endemic to China. It is characterised by its white animal coat, coat with black patches around the eyes, ears, legs and shoulders. ...

s) * ''Baylisascaris potosis'' (of kinkajous)

''Baylisascaris procyonis''

'' is found in the intestines of

s in North America, Japan and Germany. It infests 68 to 82% of some raccoon populations, according to the House Rabbit Society. According to the Michigan Department of Natural Resources, nearly 100 percent of raccoons in the Midwestern US are infected. This parasite can be extremely harmful or deadly to humans.

''Baylisascaris columnaris''

Skunks carry ''Baylisascaris columnaris'', a similar species to ''B. procyonis.'' Many pet skunks have died from this parasite. According to several skunk experts, many baby skunks from skunk farms have ''B. columnaris'' present in their bodies. The exact proportion of skunks that are infested is unknown. Since the worms are often at too early a stage in development to begin shedding eggs into the feces, a fecal test may not detect the parasite, and the pet should be pre-emptively treated with dewormers antiparasitacides. ''Baylisascaris'' eggs are highly resistant to decontamination procedures because of their dense shell and sticky surface. They can survive hot or freezing weather and certain chemicals, remaining viable for several years. Bleach can prevent the eggs from sticking, but will not ensure destruction. According to Parasitism in Companion Animals by Olympic Veterinary Hospital, hand washing is an important countermeasure against ingestion, and decontamination of other surfaces is accomplished by thoroughly flaming with a propane torch or treating with

lye Lye is the common name of various alkaline solutions, including soda lye (a solution of sodium hydroxide) and potash lye (a solution of potassium hydroxide). Lyes are used as cleaning products, as ingredients in soapmaking, and in various other c ...

. Other forms of high heat such as boiling water or steam will accomplish the same result. Children are more likely to be infected than adults because of their tendency towards pica, particularly

geophagy Geophagia (), also known as geophagy (), is the intentional practice of consuming earth or soil-like substances such as clay, chalk, or termite mounds. It is a behavioural adaptation that occurs in many non-human animals and has been documented i ...

. In spite of the numerous raccoons living in close contact with humans, less than 30 serious infections of humans by Baylisascaris had been reported by 2012; but it is thought that some cases are misdiagnosed as other infections or are never identified.

References

External links

Old Rabbit Paralysis Part III: Baylisascaris Procyonis
House Rabbit Society
Baylisascaris procyonis in Dogs
D. D. Bowman, Department of Microbiology & Immunology, College of Veterinary Medicine, Cornell University, Mar. 11, 2000.

by Matt Bolek, Diagnostic Parasitologist (link via InternetArchive, a

no longer valid).

by Olympic Veterinary Hospital.

Centers for Disease Control. * {{Authority control Parasitic diseases Animal diseases Parasitic nematodes of animals Parasitic nematodes of humans Ascaridomorpha Zoonoses Chromadorea genera Rare infectious diseases