Parasitic Insects, Mites and Ticks: Genera of Medical and Veterinary Importance/Chewing lice

Chewing lice
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Characters of Chewing lice of sub-Order Ischnocera
These lice have no blood-sucking mouthparts. They feed by chewing, using ventral mandibles like teeth. These mandibles also are used to grip onto hairs or feathers, and there is a groove in the ventral surface of the head to fit hairs or feather shafts. Palps are absent at the mouthparts.
 * Photograph shows an ischnoceran chewing louse, with the well developed ventral mouthparts arrowed.


 * Diagram of feeding at skin represents an ischnoceran chewing louse on its host (proportions of louse to skin are not accurate).

The three segments of the thorax are fused together, and the boundaries between them are indistinct. The claws of the legs do not articulate onto a distinct tibial claw (as often seen in the sucking lice). The ischnoceran lice that infest domestic animals are in two families. The Trichodectidae infest mammals: they have antennae with three segments and legs with a single claw. The Philopteridae infest birds: they have antennae with five segments and legs with a pair of claws.

Glossary

 * Chewing = The adjective 'biting' is often used as synonymous with 'chewing' and also 'sucking', as in 'biting-flies' meaning blood-sucking flies. Confusion is avoided in this book by not using biting in this sense. However, the familiar and obvious term 'biting-stress' is used here for the pruritus and pain caused to hosts by many ectoparasites (see  Sucking lice ).
 * Intermediate host = Parasitological term for a host in the life-cycle of a parasite when the parasite passes passively to the definitive host through the environment or by the intermediate host being eaten by the definitive host. (Note: insects and acarines carrying parasitic organisms between their feeding hosts are not intermediate hosts in this sense; they are vectors or transmitters because the parasitic organisms pass actively between hosts during feeding by the vector.)
 * Mandible = A pair of grasping and grinding organs forming the main part of the mouthparts, like jaws (inset on figure for Bovicola)
 * Palp = Paired, segmented, organs associated with the mouthparts, having sensory functions (2 on Heterodoxus).
 * Sclerotization = Hardening of parts of the body wall by a process of tanning.
 * Spine = A non-moveable sharp pointed extension of the body wall (see ventral head of Heterodoxus).

Bovicola (also known as Damalinia) (Trichodectidae)
Characters: female, ventral. 1- Head is short and blunt. 2- Antennae have three segments. 3- Legs have a single claw. 4- Abdomen has spiracles on the edge of the dorsal surface of segments 2 to 7. 5- Abdomen segments bear one row of short or medium setae, and other groups of setae. 6- Bands of brown sclerotization are distinct on abdominal segments. Inset: typical position of louse gripping host hair with its mouthparts. Also: body is small and light red/brown. Hosts: Bovicola bovis (Red or chewing-louse of cattle) infests cattle on their neck, shoulders, back and rump. Bovicola ovis (Red or chewing-louse of sheep) infests sheep on their back and upper regions of their body; B. caprae (Red or chewing-louse of goats) infests goats; B. equi (Horse chewing-louse) infests horses. Signs: Irritation and pruritus leads to restless self-grooming. (Note that in comparison to an infestation of sheep with psoroptic scab mites Bovicola lice do not directly cause the skin to form moist scabs, the surface of the skin will appear intact, although with heavy infestations self-grooming may damage the skin.) Disease: Biting-stress leads to loss of production from heavy infestations. Bovicola bovis feeding activity can cause damage to the appearance of processed hides. This damage is known as spot and fleck. This occurs despite the superficial feeding of these lice.

Felicola (Trichodectidae)
Characters: female, ventral. 1- Anterior part of head is elongated into a conical shape. 2- Antennae have three segments. 3- All legs have single claws. 4- Hind legs are smaller than fore- and mid-legs. 5- Abdomen has smooth appearance with a few short setae. 6- Dorsal surface of abdomen bears 3 pairs of spiracles. Also: body is small and pale yellow. Hosts: Felicola subrostrata is the only species of louse likely to be found on domestic cats.

Signs and disease: Effective self-grooming seems to protect most cats from harmful levels of infestation. However, sick, very old cats, or long-hair breeds may suffer from their infestations with this louse.

Trichodectes (Trichodectidae )
Characters: female, ventral. 1- Head is short and blunt. 2- Antennae have 3 segments. 3- Legs have a single claw. 4- Abdominal segments bear one dense row of long seta; similar setae are also on the legs. 5- Abdomen has a distinctly rounded shape. 6- Abdominal segments have spiracles on the edge of their dorsal surface. Also: body is small and pale yellow.

Hosts: Trichodectes canis (Dog chewing-louse) infests domestic dogs on their head, neck and tail. It also infests wild canids. This species may need to be distinguished from Heterodoxus spiniger on dogs in countries where both species of chewing lice occur.

Signs and disease: Heavy infestations produce irritation and biting-stress, leading to restlessness and much self-grooming. Such infestations lead to the hair-coat having a lousy appearance: matted, staring and dull. This louse is an intermediate host for the tapeworm of dogs, Dipylidium caninum. The dog becomes infected when it ingests infected lice that it has groomed off.

Goniocotes (Philopteridae )
Characters: female, ventral. 1- Antennae consist of 5 segments. 2- Head and body have a compact rounded shape. 3- Legs each bear a pair of claws. 4- Long setae project from lateral margins of abdomen. 5- Posterior margin of head bears a pair of long stout setae (like bristles) on each side. Also: body is small and pale yellow.

Hosts: Goniocotes gallinae (Fluff-louse) commonly infests poultry, amongst the down feathers over most of the body.

Signs and disease: Infestations are usually slight, but heavy infestations damage the plumage and cause restlessness leading to reduced productivity of poultry.

Goniodes (Philopteridae)
Characters: female, ventral. 1- Long setae are borne on the protruding angle at posterior of head. 2- Head is shaped distinctively with hollow margin and protruding angle posterior to the antennae. 3- Antenna consists of 5 segments. 4- Legs each bear a pair of claws. 5- Long setae project from the lateral margins of abdomen. Also: body is large and brown.

Hosts: Gonoides dissimilis (Brown chicken-louse) and G. gigas (Large chicken-louse) infests chickens, whilst G. meleagridis infests turkeys.

Signs and Disease: These lice feed on feathers and underlying skin over most parts of their host's main body. They cause irritation, pruritus, restlessness, repetitive grooming, debility, and reduced productivity.

Lipeurus (Philopteridae)
Characters: male, ventral. 1- Elongated shape is distinctive. 2- Head bears a projection just anterior to the antenna. 3- Antenna consists of 5 segments; on males its first segment is unusually long. 4- All legs have 2 claws. 5- Hind legs are twice the length of mid- and fore-legs. 6- Setae on the abdomen are sparse. 7- Two groups of long setae occur on dorsal surface of the posterior thorax. Also: body is medium size grey.

Hosts: Lipeurus caponis (Wing-louse) infests the underside of wings and tail of chickens.

Signs and disease: Irritation, pruritus, restlessness and poor growth rate are caused.

Cuclotogaster (Philopteridae)
Characters: female, ventral. 1- Head has a rounded shape, without any prominences. 2- Antenna consists of 5 segments. 3- From the posterior margin of the head project three long setae. 4- Fore-legs are shorter than mid- and hind-legs. 5- Abdominal segments each have a row of medium length setae. 6- All legs have a pair of claws. Also: body is medium sized and grey.

Hosts: Cuclotogaster heterographus (Head-louse) infests chickens on the skin and feathers of their head; sometimes extending onto the neck. Signs and disease: Young birds are particularly harmed by these lice; infestations can build up rapidly, leaving the birds weak and even killing them.

Characters of Chewing lice of sub-Order Amblycera
Lice in this group are similar in feeding habits to the ischnoceran lice because they feed with chewing mouthparts. Mouthparts are supplemented with a pair of palps next to the chewing mandibles. Antennae have 4 or 5 segments, but they are less visible than in the ischnoceran lice because they occupy an antennal groove in the head.

On the ventral surface of the head a pair of backward directed spines is usually visible. The thorax appears in two parts: the anterior segment, and the central plus posterior segments which are fused together. This division is clearest on the dorsal surface. Claws on the legs are variable, one or a pair depending on the genus. Amblyceran lice mostly parasitize birds, but also are found on marsupial mammals, and mammals in the Americas.

Heterodoxus (Boopidae)
Characters: female, ventral. 1- Head is smoothly rounded anteriorly. 2- Palps are small, and anterior to the antennae. 3- All legs end in paired claws. 4- Abdominal segments have dense arrays of long setae. 5- Abdomen is broadly rounded at posterior. Also: body is large and yellow.

Hosts: Heterodoxus spiniger infests domestic dogs and other canids, also marsupial mammals. This species may need to be distinguished from Trichodectes canis on dogs in countries where both species of chewing lice occur. Heterodoxus spiniger has also been reported infesting domestic cats but where the cats were close to heavily infested dogs.

Disease: Pathological effects are only likely if the host is already in poor condition from other parasites or malnutrition. This louse is an intermediate host of the tapeworm of dogs, Dipylidium caninum.

Distribution: Heterodoxus spiniger is considered to have evolved in Australia. It has spread to tropical and sub-tropical regions of the Americas, and to Africa.

Menacanthus (Menoponidae)
Characters: female, ventral. 1- Head is distinctly narrow anteriorly but it bulges widely at the posterior. 2- Palps and antennae are conspicuous because of narrow shape of head anteriorly. 3- All legs end in paired claws. 4- Abdomen segments have a dense array of medium length setae. 5- Abdomen is broadly rounded at the posterior. 6- Spiracles are visible at dorsal edge of abdominal segments. Also: body is large and yellow.

Hosts: Menacanthus stramineus (Chicken body-louse) infests chickens, other poultry species, aviary and game birds. Infestations are particularly dense on the breast, thighs, and around the vent.

Signs and disease: Irritation, pruritus, and restlessness cause loss of production. Infestations with the actively mobile M. stramineus can spread rapidly through a flock, and also accumulate to dense levels on individual birds. The lice may penetrate the blood vessels at base of feathers, leading to anemia. This combination of pathological effects often greatly reduces productivity of a flock. This species is the most damaging of the bird lice.

Menopon (Menoponidae)
Characters: female, ventral. 1- Head is widely and smoothly rounded at its anterior profile. 2- Palps are small, and aligned with the bases of the antennae. 3- Antennae lie within antennal grooves. 4- All legs end in a pair of claws. 5- Abdominal segments have sparse arrays of short and medium setae. 6- Abdomen is fairly narrow at the posterior. Also: body is very small and pale yellow.

Hosts: Menopon gallinae (Shaft-louse) infests chickens, turkeys and ducks on their breast and thigh feathers. It feeds only on the feathers and these lice can be seen in rows clasping a feather shaft.

Disease: Heavy infestations in young birds may be highly damaging but this louse is rarely a severe pest to adult birds.

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