Insects: Tabanids and Parasites

Tabanids

• Horse flies and deer flies are large flies that bite domestic and wild animals, humans, small mammals, and birds.
• Their mouthparts are adapted for slashing and sponging, resulting in painful bites.
• Deer flies are particularly known to bite horses in shaded areas.

Melophagus ovinus

• This species is a common parasite of sheep.
• It is a flattened, hairy, and wingless fly that sucks blood from the host.
• The entire life cycle occurs on the host, making it difficult to control.
• It may be mistaken for ticks due to its shape and flattened body.

Cuterebra spp.

• These are rodent and rabbit bot flies, also known as New World skin bot flies.
• They are zoonotic, meaning they can infect multiple hosts, including humans.
• Larvae develop in subcutaneous connective tissue, causing irritation and swelling.
• The third instar larvae must be manually removed, and this can sometimes cause severe allergies (Type I hypersensitivity).

Hypoderma spp.

• Adults of this species are known as warble flies, heel flies, or ox warbles.
• Larvae are known as cattle grubs.
• The primary host is cattle.
• First instars of H. lineatum develop in the submucosa of the esophagus, while H. bovis larvae develop in the epidural fat of the spinal cord.
• Third instar larvae create characteristic lumps on the backs of cattle.
• Timing treatment is crucial for effective control.

Oestrus ovis

• This fly is known as the sheep nasal bot.
• It parasitizes sheep and is occasionally zoonotic.
• First instar larvae are deposited by the female during flight directly into the host's nasal passages.
• Larval irritation causes “snotty nose” in sheep.
• In rare cases, larvae can migrate abnormally, potentially reaching the brain.

Gasterophilus spp.

• These bot flies parasitize horses.
• Larvae develop in the stomach or small intestine, causing discomfort and irritation.
• Different species can be differentiated based on the color and spines of their larvae.
• Adult flies are often referred to as "fly worry" as they are known to constantly harass horses.

Cochliomyia hominivorax

• This fly is commonly known as the screwworm.
• It infests livestock and wildlife.
• It is a 10 mm long, bluish-green fly with three stripes on its thorax and orange-brown eyes.
• Adults mate only once in their lifetime.
• Female flies lay eggs on fresh, uninfected wounds.

Cochliomyia hominivorax Life Cycle

• Larvae infest and feed on living tissue.
• They are a serious threat to livestock and wildlife, causing rapid tissue damage and death.
• The infestation typically starts with fresh wounds that attract female flies.
• The infested area develops a foul odor and quickly becomes infected.

Cochliomyia hominivorax Diagnosis and Treatment

• Diagnosis is typically made by recognizing the maggots in lesions.
• Prompt reporting to veterinary authorities is crucial.
• Treatment involves disinfecting wounds and releasing sterile male flies.
• Screwworm outbreaks are a major concern, and recent outbreaks in Florida highlight the importance of monitoring and control.

Sarcophagidae

• These flies are commonly known as flesh flies.
• They are found worldwide and can infest any animal.
• Adults are twice the size of house flies.

Sarcophagidae Life Cycle

• Females lay first instar larvae in sores, wounds, and necrotic tissues.
• Larvae develop into third instars and then leave the host to pupate.
• Pupae are the overwintering stage.
• The primary sites of infestation are skin and wool.

Sarcophagidae Prevention and Control

• Prevention involves maintaining good hygiene and husbandry practices, including sanitation, improved housing, and tail docking.
• Promptly treat wounds to prevent fly infestation.

Ischnocera (Mallophaga)

• These are chewing lice, characterized by their biting mouthparts.
• They are host-specific and spend their entire life cycle on the host.
• They typically feed on skin, hair, feathers, and other organic material.
• They are relatively small, approximately 3 mm long, and have a yellowish color.
• They move rapidly over the host's skin and covering.

Trichodectes canis

• This louse is commonly known as the dog biting louse or canine chewing louse.
• It parasitizes dogs.
• It is yellowish, with biting mouthparts.
• It is an active louse, with adults reaching 2 mm in length.

Trichodectes canis Life Cycle

• Females lay eggs, which develop into nymphs and eventually adults.
• They require a host to complete their life cycle.

Trichodectes canis Pathogenesis and Clinical Signs

• Heavy infestations are common in neglected and underfed dogs, especially young animals.
• They are known to transmit Dipylidium caninum (a tapeworm) to dogs.
• The primary clinical sign is severe itching (pruritus), which causes dogs to scratch excessively, leading to hair loss.

Trichodectes canis Diagnosis and Treatment

• Diagnose by identifying the louse.
• Treatment involves avoiding contact with infected brushes, combs, and blankets, and administering macrocyclic lactones.

Felicola subrostratus

• This is the common cat biting louse.
• It parasitizes cats.
• It is beige or yellow, with transverse brown bands.
• The head is triangular, and the legs are small.
• Adults are 1-1.5 mm long.

Felicola subrostratus Pathogenesis and Diagnosis

• Infestations are more common in elderly or chronically ill cats, and longhaired breeds are particularly susceptible.
• Diagnose by identifying the louse.

Bovicola (Damalinia) bovis

• This louse is the cattle biting louse.
• It parasitizes cattle.
• It is a typical Ischnoceran louse, with a reddish-brown color.
• The primary site of infestation is the head, poll, neck, shoulders, rump, and tail switch.

Bovicola (Damalinia) bovis Life Cycle

• Louse numbers are highest during winter, with dense coats, indoor housing, and parthenogenesis.
• Numbers are lower in summer due to thin coats, higher skin temperatures, and sunlight being lethal to lice.

Bovicola (Damalinia) bovis Pathogenesis and Clinical Signs

• In large numbers these lice cause chronic dermatitis, irritation, itching, and pruritus.
• They can negatively affect the host’s body condition and fleece quality.
• Their presence can also be a secondary sign of malnutrition or chronic disease.

Bovicola (Damalinia) bovis Diagnosis and Treatment

• Diagnose by identifying the louse.
• Treatment involves administering various ectoparasiticides, including macrocyclic lactones.

Bovicola (Damalinia) ovis

• This louse is the biting louse of sheep.
• It parasitizes sheep.
• It is a typical Ischnoceran louse.
• It is the most pathogenic of all sheep lice, causing damage to fleece and attracting blow flies.

Bovicola (Damalinia) ovis Diagnosis and Treatment

• Diagnose by identifying the louse.
• Numerous treatments are effective.

Bovicola (Damalinia) caprae

• This louse is known as the red louse.
• It parasitizes goats.
• It is similar to Bovicola ovis.

Bovicola (Damalinia) equi

• This louse parasitizes horses and is similar to Bovicola ovis.

Ischnocera - Avian Lice

• These are biting and chewing lice that parasitize domestic and wild birds.
• There are over 40 species of these avian lice.
• The primary site of infestation can vary, with lice being categorized based on their preferred location, such as the wing or body.

Ischnocera - Avian Lice Pathogenesis and Clinical Signs

• Lice digest keratin and bite feathers.
• Infestation causes sleeplessness, loss of appetite, scratching, and feather plucking.
• Secondary effects, such as bacterial or fungal infections, can be more serious than the direct damage caused by lice.

Ischnocera - Avian Lice Diagnosis

• Diagnose by identifying the louse.