Farm animal dermatology Flashcards
What are skin disease causes in farm animals?
- Ectoparasites
- Bacteria
- Viral
- Fungal
- Prion
- Nutritional
- Toxic
- Stress
What symptom is common to all ectoparasites?
- pruritus - if it scratches, think parasites
What is dermatophytosis? What animals are more likely to be affected? How is it diagnosed? How is it treated?
Trichophyton verucosum (ringworm)
* Commonly seen in young calves and often self-limiting (although may take months to resolve)
* Zoonotic
* Animals suffering from poor nutrition or immunosuppressed (BVD) are more likely to be affected
* Can survive in buildings for many months - lesions often resolve once animals are turned out
* Diagnosis based on clinical signs or microscopic evaluation of spores on hair plucks
* Treatment may include topical enilconazole and/or vaccination (Ringvac - currently unavailable)
What are the important ectoparasites of cattle?
- lice (4 species)
- mites (chorioptes mainly on tail, head)
- ticks (vector for TBF and babesia
- flies (vector for moraxella bovis and summer mastitis pathogens)
What are the important ectoparasites of sheep?
- Psoroptes ovis (sheep scab mite) – Severe and contagious
- Myiasis (blowfly strike) – massive welfare concern
- Lice – Less severe than sheep scab but associated with debility and weight loss
What are the 3 cattle lice species? How are they treated?
Cattle lice species
* Bovicula bovis
◦ most common
◦ chewing louse
◦ usually on the head
* Linognathus vituli
◦ sucking louse
◦ around the head area
* Haematopinus eurysternus
◦ sucking louse
◦ around the horns
Cattle lice treatment
Options
* Pour-on synthetic pyrethroid preparation such as deltamethrin (sucking and biting lice)
* Pour-on group 3-ML anthelmintics (ivermectin, doramectin and eprinomectin) (sucking and biting lice)
* Injectable group 3-ML anthelmintics (ivermectin, doramectin and eprinomectin) will remove all sucking lice and >98% of biting lice
All cattle in direct contact must be treated. Treat at start of winter housing period if cattle are at risk.
Most treatments aren’t effective against eggs so may need repeat treatments after 2 weeks to kill nymphs.
What causes pinkeye in cattle? What are the 4 stages of the disease? How is it treated? How is it prevented?
Infectious bovine keratoconjunctivitis
- Agent: the bacteriumMoraxella bovis
- Vector: Face fly
- Signs: corneal ulcers, oedema, lacrimation, opacity, epiphora
- Stage 1 - tearing, lacrimation, photophobia, small central corneal ulcer
- Stage 2 - ulcer spread across the cornea, cloudy cornea, neovascularisation, pink cornea
- Stage 3 - ulcer spreads, inner eye fills with fibrin and WBC, eye looks yellow/brown
- Stage 4 - ulcer covers entire cornea, iris adhesions
- Treatment:
◦ Antibiotics
‣ Routes; IM, SC, topical, subconjunctival
◦ NSAIDs - Prevention:
◦ Fly control with topical SP
‣ e.g. Permethrin
◦ Biological control
‣ Friendly flies/parasitic wasps
What is onchocerca? How is it treated?
- Thin, white worms found in the eye of cattle
- Vectors: blackfly or cullicoides
- Ocular infection:
◦ ranging from acute oedematous necrosis to chronic granulomatous changes
◦ results in marked fibrosis and mineralization. - Treatment:
◦ Systemic ivermectin
◦ Anti-inflammatories - Not in the UK
Describe the life cycle of a warble fly. What is the impact of warble fly? How is it treated?
- Hypoderma bovis and Hypoderma lineatum
- Have very similar life cycles
- Adult warble flies are hairy and about the size of a small bee with yellow/orange abdomens.
- They lay eggs on the hair of cattle in summer, larvae hatch and migrate into the skin then travel to the oesophagus and spinal cord where they lay dormant over winter.
- In spring they travel back under the skin, mature for around 30 days then drop off and pupate in the soil.
- The warble fly emerges around 36days later.
- Impact of warble fly
◦ Gadding behaviour: Flies cause harassment to cattle, which become
‣ (1) restless leading to physical injuries
‣ (2) depressed, leading to decreased production and growth
◦ Ectopic migration & Paralysis
◦ Damage caused by warbles
◦ Downgrade of the hide caused by perforations of skin by breathing larvae
◦ Reduced reproduction: caused by large number of warbles under skin in spring - Treatment:
◦ OPs - 98% effective in autumn and less efficient in spring
ND in Scotland
What mites are cattle most prone to? How are they diagnosed? How are they treated?
surface mites
* Chorioptes most common (tail mange, leg mange, scrotal mange)
* Characteristic locations
* Deep skin scrapes still required to get a good sample from the edge of a lesion
* Sharp scalpel – scrape until you get capillary ooze
* Treatment is Permethrin (Synthetic pyrethroid) or pour on Macrocyclic lactones (injectable less effective).
* Scrotal mange may impact fertility.
* Following treatment also need to move animals from infected area.
What ticks are livestock prone to? What is their life cycle? What are the consequences of tick infestations? What diseases do they carry? What steps can be taken for host and environmental control?
- ixodes ricinus and haemaphysalis punctate
Consequences of tick infestations
* The main risk they pose is as a vector for disease, but bites can cause inflammation and hypersensitivity.
* Poor body condition
* Weight loss & reduced milk yields
* Hide/fleece damage – reduction in quality
* Intense irritation – associated behavioural issues
* Lesions may form around areas of bites – in some instances opportunistic bacterial infections may occur
* Prolonged infestation may result in small granuloma formation due to retention of mouth parts or salivary secretions
Ticks as vectors
- tick borne fever
- babesiosis
- flavivirus (encephalitis)
Host Control
* Some pour on pyrethroids or MLs?
◦ none in the UK licensed for ticks in cattle
◦ Need to be reapplied at regular intervals
◦ Impact on GI worms
Environment Control
* Active and start to feed in early spring
◦ start and duration difficult to predict precisely
‣ Avoid tick prone pastures if possible?
◦ Attempts to decrease tick population = pasture improvement
‣ drainage and scrub clearance
◦ Not able to use acaricide
Treatment may include blood transfusion/imidocarb (NB very long withdrawal).
Control challenging as ticks spend most of their life cycle off the host.
What is photosensitisation in cattle? What are the clinical signs? How is it diagnosed? How is it treated? How can it be prevented?
Occurs when the presence of a chemical makes skin become sensitive to sunlight (particularly UV wavelengths). This leads to skin damage and loss, particularly in unpigmented areas.
Aetiology
1. Direct photosensitisation occurs when the chemical comes from a defect in the animals metabolism of its red blood cells, or, more commonly, from plants such as St. John’s wort.
2. Secondary photosensitisation occurs in animals with liver damage. This damage interferes with the complete breakdown of chlorophyll, resulting in the accumulation of a photosensitive chemical.
3. Local photosensitivity can also result as a reaction to the sap of some plants.
Most commonly affected sites are those exposed to direct sunlight, including the udder (which is exposed when the animal lies down).
Clinical Signs
* Non-pigmented skin affected
* Hair loss, reddening, peeling
* Ulceration of skin
* Crusting, bleeding
Diagnosis
* On the clinical signs described above
Treatment
* Removal to cool shaded housing
* Fly control
* Supportive therapy
Prevention
* Do not breed from animals with photosensitisation due to a genetic defect.
* Identify and remove possible plant sources of photosensitising chemicals
