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Ancylostoma caninum

By Sophia Saeed

Geographic Range

Ancylostoma caninum is cosmopolitan in warm and temperate climates, especially where there is adequate moisture. (Marquardt, 2000; Olsen, 1974)

Habitat

The first larval stage lives in the soil where it molts twice and then emerges into its infectious third stage. The third stage juvenile is either ingested, in which case it goes through the stomach and ends up in the small intestine, or it enters via the skin. If A. caninum enters through the skin of the host, it finds its way to the circulatory system which takes it to the trachea. In the trachea, the juvenile is swallowed and ultimately ends up in the small intestine.

In abnormal hosts, such as humans, A. caninum larva cannot remain in the subcutaneous layer of the skin, unable to enter the circulatory system to complete its life cycle. (Marquardt, 2000; Olsen, 1974)

Physical Description

Ancylostoma caninum is usually gray, but appears reddish if there is blood in its alimentary canal. The body is covered by a non-living cuticle that sheds at molts allowing for growth of the nematode. A male is 10 to 12 mm long and 0.36 mm wide; a female is 14 to 20 mm long by 0.5 mm wide and has a pointed tail. The anterior end is bent dorsally so that the arrangement of the hookworm's ventral and dorsal sides are reversed. In the head of the hookworm is an area called the buccal capsule which contains one the mouth and teeth. Ventrally, there is one pair of teeth, each with three points. In the depth of the capsule there is a pair of triangular dorsal teeth and a pair of ventro-lateral teeth. At its posterior end, a male A. caninum has a prominent bursa. The rays inside the bursa are used in identifying species of hookworms, so A. caninum has a particular arrangement of rays in its bursa. The female reproductive organ, the vulva, is found near the junction of the second and last thirds of the body. (Cheng, 1973; Jones, 1967; Marquardt, 2000; Olsen, 1974)

  • Sexual Dimorphism
  • sexes shaped differently
  • Range length
    10 to 20 mm
    0.39 to 0.79 in

Development

The eggs of Ancyclostoma caninum pass through several larval instars before becoming an adult. In an environment of 23 degrees Celsius, the egg hatches into the first-stage juvenile in the soil in approximately one day. Within four to five days, the cuticle is molted twice and the infective third-stage juvenile emerges. Infection of the host can occur through ingestion or by penetration of the unbroken skin but either way, the parasite ends up in the small intestine of the host. If ingested, A. caninum travels to the stomach of its host, molts, migrates to the small intestine, molts a fourth and final time, and develops to maturity in about 5 weeks. If entrance is via the skin, A. caninum makes its way through the dermal layers and enters the circulatory system which takes it to the lungs. Once in the lungs, A. caninum leaves the capillaries and travels up the trachea where it is swallowed. It then goes through the same cycle that ingested A. caninum go through until it reaches the small intestine.

Copulation occurs within the small intestine and the female worms pass eggs in the feces. Transplacental and transmammary transmission are known for dogs infected with A. caninum. Occasionally, an A. caninum juveniles will penetrate the skin of a human but cannot complete its life cycle in the inappropriate host. The juvenile wanders about in the upper layers of the skin, causing a conditio called dermal larva migrans. (Marquardt, 2000; Olsen, 1974)

Reproduction

Nematode females may produce a phermomone to attract males. The male coils around a female with his curved area over the female genital pore. The gubernaculum, made of cuticle tissue, guides spicules which extend through the cloaca and anus. Males use spicules to hold the female during copulation. Nematode sperm are amoeboid-like and lack flagella.

Copulation for Ancylostoma caninum occurs within the small intestine and the female worms pass eggs in the feces. (Barnes, 1987; Marquardt, 2000; Olsen, 1974)

There is no parental investment beyond egg laying.

  • Parental Investment
  • pre-fertilization
    • provisioning

Behavior

Ancylostoma caninum is not a social parasite. The rate of infection is temperature dependent: temperate and warm climates are optimal conditions while cooler temperatures decrease the rate of infection. (Marquardt, 2000)

Communication and Perception

Nematodes in general have papillae, setae and amphids as the main sense organs. Setae detect motion (mechanoreceptors), while amphids detect chemicals (chemoreceptors).

Females may produce a phermomone to attract males. (Barnes, 1987)

Food Habits

These hookworms live in the small intestines of many animals, predominantly dogs. Other hosts are cats, foxes, wolves, and other carnivores in temperate as well as tropical and subtropical areas. On very few occasions have humans been reported as hosts. Ancyolostoma caninum feeds primarily on the tissue of the small intestine but is also known to suck blood. Adult worms feed at approximately six different sites per day. (Chowdhury and Tada, 1994; Lapage, 1962; Marquardt, 2000; Olsen, 1974; Roberst and Janovy Jr., 2000)

  • Animal Foods
  • blood
  • body fluids

Predation

These parasites are probably not preyed on directly, but are ingested from host to host. Larval mortality is high as most of the parasites do not reach appropriate hosts.

Ecosystem Roles

These hookworms live in the small intestines of many animals, predominantly dogs. Other hosts are cats, foxes, wolves, and other carnivores in temperate as well as tropical and subtropical areas. On very few occasions have humans been reported as hosts.

Species Used as Host

Economic Importance for Humans: Negative

It is difficult to assess the economic importance of Ancylostoma caninum because they do not infect animals raised for food or labor purposes very often. Domestic dogs, the most common host, can suffer from anemia. If proper precautions are not taken, pet owners with infected dogs can become the host of Ancylostoma caninum. Since infected dogs pass A. caninum larvae out with their feces, anyone who comes in direct contact with feces can obtain the parasite. For example, if a barefoot child is playing in the yard where his infected dog has passed feces, the larvae of A. caninum can enter the child's body via contact of the feet with the feces. Once in the child, an A. caninum will migrate within the subcutaneous layer of the skin for several months causing a condition called dermal larva migrans. (Marquardt, 2000)

Contributors

Renee Sherman Mulcrone (editor).

Sophia Saeed (author), University of Michigan-Ann Arbor, Solomon David (editor), University of Michigan-Ann Arbor.

Glossary

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

World Map

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

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Neotropical

living in the southern part of the New World. In other words, Central and South America.

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Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

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agricultural

living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

causes disease in humans

an animal which directly causes disease in humans. For example, diseases caused by infection of filarial nematodes (elephantiasis and river blindness).

causes or carries domestic animal disease

either directly causes, or indirectly transmits, a disease to a domestic animal

chaparral

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

chemical

uses smells or other chemicals to communicate

cosmopolitan

having a worldwide distribution. Found on all continents (except maybe Antarctica) and in all biogeographic provinces; or in all the major oceans (Atlantic, Indian, and Pacific.

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

internal fertilization

fertilization takes place within the female's body

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

World Map

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

parasite

an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

scrub forest

scrub forests develop in areas that experience dry seasons.

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

suburban

living in residential areas on the outskirts of large cities or towns.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

urban

living in cities and large towns, landscapes dominated by human structures and activity.

References

Barnes, R. 1987. Invertebrate Zoology. Orlando, Florida: Dryden Press.

Cheng, T. 1973. General Parasitology. New York: Academic Press.

Chowdhury, N., I. Tada. 1994. Helminthology. Delhi: Rajkamal Electric Press.

Jones, A. 1967. Introduction to Parasitology. USA: Addison-Wesley Publishing Co..

Lapage, G. 1962. Mönnig’s Veterinary Helminthology and Entomology. Baltimore: The Williams and Wilkin Company.

Marquardt, W. 2000. Parasitology and Vector Biology. USA: Harcourt Academic Press.

Olsen, O. 1974. Animal Parasites: Their Life Cycles and Ecology. Baltimore: University Park Press.

Roberst, L., J. Janovy Jr.. 2000. Foundations of Parasitology. USA: McGraw-Hill Higher Education.

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