Dermatophilus congolensis - 20% Flashcards
Etiology (dermatophilus)
Dermatophilus congolensis (gram positive, aerobe or facultative anaerobe, cocci that is a normal dermal inhabitant of several species, including sheep, horses, and cattle)
Filamentous hyphae and motile zoospores.
Dogs and cats are usually not primary hosts but can be naturally infected.
Cattle- streptothricosis
Horse- rain scald
Sheep- lumpy wool
Goats- strawberry foot rot
Pathophysiology (dermatolphilus)
Chronic moisture, trauma, ectoparasites, and immunosuppression may predispose a patient to disease since the organism typically cannot penetrate intact epithelium.
Spread by direct contact between animals, through contaminated environments or possibly via biting insects.
Asymptomatic chronically infected animals are considered primary reservoir
Prolonged wetting by rain, high humidity, high temp, various ectoparasites that reduce or permeate natural barriers of integument influence development, prevalence, seasonal incidence, and transmission
Ticks and lice – major predisposing factors in cattle and sheep
Epidemics during rainy season – moisture facilitates release of zoospores from preexisting lesions and subsequent penetration of epidermis and est of new foci of infection. High humidity contributes indirectly to spread of lesions by allowing increases of number of biting insects, particularly flies and ticks – mechanical vectors
Shearing, dipping, or introducing infected animal into herd/flock can spread infection.
Contagious – reduction in systemic or local skin resistance favors est of infection and subsequent disease where zoospores must reach a skin site where norm protective barriers reduced or deficient
Resp efflux of low conc of carbon dioxide from skin attracts motile zoospores to susceptible areas on skin surface – zoospores germinate to prod hyphae which penetrate living epidermis and spread in directions> Hyphal penetration causes acute inflamm reaction
Dogs and cats can develop dermatophilosis from contact with large animals or from the environment.
clinical signs (dermatophilus)
Skin lesions are found on the haired portion of the skin. Lesions are most commonly found on the dorsum of the body, and over the scapula and lateral thigh. The head and ears can also be affected. Lesions start as erythematous papules with crusts. Crusts are typically thick, gray-yellow, and adherent. Hair is usually embedded into the crust.
Purulent exudate and a bleeding, ulcerated surface is seen underneath the crust.
Deaths occasional in calves and lambs bc generalized dz with or without secondary bact infection and secondary fly or screwworm infestation
Damaged hides in cattle, wool loss in sheep, lameness and loss of performance in horses
Cattle: hairs mat together as paint brush lesions, crust or scab formation as initial lesions coalesce, accum of cutaneous keratinized material forming wart like lesions – raised, matted tufts of hair
Dairy cows – popular crusted lesions on udder
Biting fly lesions – primarily on back; ticks – head, ears, axillae, groin, scrotum
Chronic lumpy wool infections – pyramid shaped masses of scab material bound to wool fibers Crusts primarily on dorsal areas of body, prevent shearing of sheep
Treatment (dermatophilus)
Bathing and removing crusts
Susceptible to wide range of antimicrobials – erythromycin, spiramycin, pen G, ampi, chloramphenicol, streptomycin, amoxicillin, tetracyclines, and novobiocin
Two doses of long acting oxytetracycline 1 day apart – curative in 85% of cattle and 100% of sheep
Food producing animals – topical application of lime sulfur – cost effective
Insecticides externally to control biting insects
Horses: soak lesions gently and remove, topical abx shampoo effective as adjuvant, chlohex recommended, topical tx with iodine superior to parenteral oxytetracycline alone
Penicillin, amoxi and doxy
Prevention/ response (dermatophilus)
Isolate clinically affected animals, cull affected animals, control ectoparasites
Prevent chronic maceration of skin and keep animals dry
Check zinc levels – outbreaks assoc with zn deficiencies
Direct contact with infected animal – can lead to infections on hands and arms
Handle with gloves and thorough handwashing with antibacterial soap
