Like most species of lice, members of the family Trichodectidae have hair-like appendages that extend from the antennal segments. The lice use these structures for perception; they function to help lice sense their surroundings. A number of chewing lice also have chemoreceptors located on the antennae.
Perception Channels: tactile ; chemical
There are no known predators of Trichodectes canis although this species may sometimes be unintentionally swallowed by the host during grooming or by humans who come into contact with infected pet dogs.
Trichodectes canis is a small, chewing louse species in which members are flat-bodied and do not have wings. Females are typically larger than males with body lengths ranging from 1.75 to 1.82 mm in females and 1.60 to 1.68 mm in males. However, T. canis specimens discovered on raccoon dogs differed in body length from those found on domestic dogs, which suggests that polymorphisms also exist between lice in different habitats. Females of the genus Trichodectes can also be characterized by a special organ that grows from underneath the end of the abdomen. When viewed from above, portions of this structure peak out from under the abdomen resembling two curved appendages occurring on either side of the genital region. Females use this appendage for two purposes: to help glue their eggs to hosts' hair and to grip the fur in order to stay on the host. Members of the genus Trichodectes typically have antennae with three segments. However, in the family Trichodectidae sexual dimorphism occurs in the antennae, often resulting in differences in the size or shape of the antennal segments. Species in the family Trichodectidae are also characterized by having a single claw at the end of each tarsus. As in all Ischnocerans, T. canis has a pair of mandibles but has lost the maxillary palps. In addition, Trichodectes species are known to have retained a pair of degenerate eyes.
Range length: 1.60 to 1.82 mm.
Other Physical Features: ectothermic ; bilateral symmetry ; polymorphic
Sexual Dimorphism: female larger
Generally, the life cycle of Trichodectes canis takes 3 to 5 weeks to complete. Longevity has not been determined, however males have been speculated to have shorter life-spans when compared to females.
Trichodectes canis is a permanent parasite; therefore all life stages of this parasite live on the host. It is most commonly found living on domestic dogs, but has also been found on other canine species in the wild including coyotes, gray wolves and golden jackals. A couple of studies also noted that T. canis is more prevalent in canid hosts that are extremely young or old, or those that are unhealthy. Trichodectes canis prefers to live on certain areas of the host such as the back, the head and the neck.
Habitat Regions: temperate ; tropical ; terrestrial
Terrestrial Biomes: forest
Other Habitat Features: urban ; suburban
Trichodectes canis is known to inhabit many regions worldwide and is able to tolerate varying extremes of temperature. It has been noted that T. canis is not a native species of Australia but was brought in with domesticated animals. In northern areas like Scandinavia, T. canis is believed to be a major ectoparasite of dogs because the climate is too cold to harbor the presence of other ectoparasites such as fleas or ticks.
Biogeographic Regions: nearctic ; palearctic ; ethiopian ; neotropical ; australian (Introduced )
Trichodectes canis is parasitic on canid species. Although domestic dogs are the primary hosts, it has been noted as a parasite on a number of different species including: gray wolves, coyotes, golden jackals, Patagonian foxes, crab-eating foxes, Bengal foxes, civets, and raccoon dogs. Trichodectes canis survives off of these hosts by consuming bits of skin from the surface of the host, or fluids produced by the skin. The skin particles are collected through the use of modified mouthparts that are used to scrape the surface of the skin. Species in the genus Trichodectes also have mouthparts that allow them to bite host skin.
Animal Foods: mammals; body fluids
Primary Diet: carnivore (Eats body fluids)
As an ectoparasite of canids, Trichodectes canis can make the host more prone to disease by causing stress to the animal. This stress occurs as a result of increased hair loss and by the presence of wounds on the surface of the skin. These physical manifestations occur during host grooming which increases in response to growing louse populations which increases the itching sensations caused by the lice feeding. These factors may cause problems for hosts that live in colder climates by weakening the host’s tolerance for the cold. In addition to the physical damage, T. canis can also serve as an intermediate host for Dipylidium caninum which is a tapeworm of dogs.
Ecosystem Impact: parasite
Species Used as Host:
Commensal/Parasitic Species:
There are no known beneficial impacts of Trichodectes canis on humans.
When present in high populations, Trichodectes canis can be the cause of many adverse effects in household dogs. These effects include extreme hair loss and multiple scratches or wounds on the surface of the host’s skin, which are a result of scratching by the host. The host reacts this way because of the discomfort caused by the feeding habits of T. canis. As a result, this parasite has an adverse effect on humans economically, forcing pet owners to spend money on various veterinary medications to help alleviate the discomfort. Trichodectes canis can also serve as an intermediate host for dog tapeworms. Humans, who come into contact with a dog infested with T. canis and mistakenly consume the louse, may also be infected with dog tapeworms.
Negative Impacts: causes or carries domestic animal disease
After laying the eggs, called nits, the female glues them to individual hairs on the host. Nits typically take 5 to 8 days to hatch. In the genus Trichodectes, nits have a cover which the larva pushes open when leaving the egg. The life cycle of T. canis consists of three stages of nymphs which morphologically resemble the adults, except for being smaller in size. The third nymph then turns into a sexually mature adult. In general, lice in the order Phthiraptera molt after each nymphal stage to proceed to the next stage. The entire life cycle takes around 3 to 5 weeks and takes place completely on the host.
Development - Life Cycle: metamorphosis
Currently there are no conservation concerns regarding Trichodectes canis. Many efforts are being made to reduce population numbers to reduce the spread of disease and discomfort inflicted on domestic dogs.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
Trichodectes canis and another canine louse species Heterodoxus spiniger are not usually observed on the same host. The reason for this is that T. canis is competitively excluded by H. spiniger.
Currently, mating systems for this species are poorly understood. Mating may occur year-round, and the male, who is the smaller of the two sexes, initiates this process by moving underneath the female and lifting its genital region up towards the female.
In lice, mating occurs between adult males and females year-round. Triatoma dimidiata reaches the stage of the sexually mature adult at around 3 to 5 weeks. This species of louse tends to mate on the host. Sometime after mating occurs, the female will glue her eggs onto the hairs of the host. The young will hatch 5 to 8 days after being laid.
Breeding interval: Exact breeding interval for Triatoma dimidiata is unknown.
Breeding season: Triatoma dimidiata breeds year-round.
Range gestation period: 5 to 8 days.
Range age at sexual or reproductive maturity (female): 3 to 5 weeks.
Range age at sexual or reproductive maturity (male): 3 to 5 weeks.
Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); oviparous
Trichodectes canis exhibits no parental involvement.
Parental Investment: no parental involvement
Trichodectes canis, also known as canine chewing louse, is a chewing louse found on domesticated dogs and wild canids throughout the world. T. canis is a well-known vector for the dog tapeworm, Dipylidium caninum. T. canis usually does not present any major problems to the host, however, can be very irritating in heavy infestations. In North America and most developed countries, T. canis infestation of domesticated dogs is very uncommon as long as they are properly cared for and healthy. Poorly taken care of dogs are more prone to getting a lice infestation.
Trichodectes canis is a louse of the suborder Mallophaga, or chewing lice. T. canis is a small, flat-bodied louse. Males are typically smaller than females, with body lengths ranging from 1.60 to 1.68 mm in males and 1.75 to 1.82 mm in females. Females also differ from males in the fact that they possess a special organ that is located from underneath the end of the abdomen. This organ, when seen from above, resembles two bowed appendages on either side of the genital region. This organ serves two purposes – in helping to glue the eggs to hosts' fur, and to grasp fur in order to remain on the host. As a member of the genus Trichodectes, T. canis usually have antennae with three segments and a single claw at each tarsus. The mouthparts of the T. canis include a pair of mandibles lacking the maxillary palps. In addition, T. canis possess a pair of degenerate eyes and hair-like appendages from their antennae that function for perception. Other physical features include being ectothermic, possessing bilateral symmetry, and polymorphic.
Trichodectes canis, known for their ability to tolerate extremes in temperature, are found in many different regions worldwide. T. canis was originally found on domesticated dogs in the Czech Republic in the 1950s. However, this louse has been found on wild canines as well – on gray wolves in Canada (1934), and coyotes in Texas and Kansas (1959). In addition to the domestic dog, T. canis is known to inhabit C. lupus, C. aureus, C. latrans, Dusicyonculpaeus, Cerdocyonthous, Vulpesbengalensis and Viverracivetta as well. T. canis is understood to have been brought to Australia with the domesticated dog. T. canis is said to be a major ectoparasite of domesticated dogs in colder regions such as Scandinavia because the environment is too harsh to foster the growth of other ectoparasites such as ticks or fleas.
Trichodectes canis lives in temperate, terrestrial, and tropical habitats, both urban and suburban. T. canis lives all stages of life on the host. Therefore, T. canis is known as a permanent parasite. T. canis is known to live on domesticated dogs, but also several other hosts:
It has also been noted that T. canis is more likely to choose hosts who are older, younger, or otherwise unhealthy. T. canis is known to prefer to inhabit the back, neck, and head of the host. Transmission of T. canis to domesticated cats or humans is not expected to occur.
After laying the nits (eggs), the female glues each to a single hair on the host. After five to eight days, the nits hatch from the egg as the larva push the covering of the nit open (the operculum) when parting from the egg. Females lay up to 100 nits at a time. There are three molts that occur, each nymph resembling the adult but with increasing size. The third nymph then becomes a mature adult. The life cycle of T. canis occurs within three to five weeks, occurring entirely on the host. The longevity of T. canis is unknown, however, females are thought to live longer than males.
Currently, little is known regarding the mating systems for Trichodectes canis. Mating is believed to ensue year-round. The male initiates the mating process by positioning himself under the female and lifting his genitals up towards the female. T. canis has no parental involvement.
Although Trichodectes canis is a permanent parasite, males may be more mobile than females in regards to leaving the host. T. canis exhibits high preference for hosts within the canine species, however, appears to have no real preference for different species of canines. When inhabiting hosts that are unhealthy or live in the wilderness, T. canis is able to build up large populations. However, domesticated dogs do not usually build up these large infestations. T. canis has several adaptations that better suit it to being a permanent parasite. The females' modified legs, mandibles, and abdominal appendages allow them to grip to fur easily. T. canis tend to move much slower than human lice, and may appear almost motionless.
Trichodectes canis survives by consuming flakes of skin and fluids produced by their canine hosts' skin. T. canis' modified mouthparts including mandibles with no maxillary palps are used to scrape the hosts' skin to feed.
Trichodectes canis may cause the host to become stressed, resulting in an increased risk of contracting infectious diseases. T. canis causes stress by creating wounds on the surface of the hosts' skin. The host also experiences hair loss as a result of increased host grooming in response to the itching feelings of the lice feeding. These problems may be magnified by colder environments. T. canis is also a known intermediate host for Dipylidium caninum, or canine tapeworm. Dipylidium caninum is spread by the consumption of T. canis. Should a human accidentally consume the louse, they may contract the tapeworm as well, although most cases are asymptomatic.
Infestations of Trichodectes canis are treated according to typical lice infestations in dogs. Imidacloprid and selamectin administered is effective, as well as topical permethrin. Treatment of domesticated dogs is usually very successful, as T. canis has no environmental involvement.
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Trichodectes canis, also known as canine chewing louse, is a chewing louse found on domesticated dogs and wild canids throughout the world. T. canis is a well-known vector for the dog tapeworm, Dipylidium caninum. T. canis usually does not present any major problems to the host, however, can be very irritating in heavy infestations. In North America and most developed countries, T. canis infestation of domesticated dogs is very uncommon as long as they are properly cared for and healthy. Poorly taken care of dogs are more prone to getting a lice infestation.
