Skin Diseases of Cattle in the Tropics

A Guide to Diagnosis and Treatment

Mohamed Elamin Hamid

• Publisher: Academic Press
• Year: 2016
• Print ISBN: 9780128110546
• eBook ISBN: 9780128110553
• Topic: Medicine
• Subtopic: Medical Microbiology & Parasitology

Skin Diseases of Cattle in the Tropics: A Guide to Diagnosis and Treatment is a clinical and practical guide to help animal scientists, field veterinarians, veterinary students, and technicians make appropriate and differential diagnoses. It features quizzes of clinical cases, along with multiple images of characteristic lesions and laboratory findings of major skin diseases (and diseases with skin manifestations) that are prevalent in tropical areas, notably the Sub-Saharan African countries. This self-learning and easy-to-use instructional guide, a unique offering in the field of animal science and veterinary medicine, provides essential and foundational information about relevant skin conditions that are followed by illustrated flow charts of laboratory diagnoses and summaries of respective diseases. This title makes the subject accessible for practicing veterinarians and animal scientists, and is particularly useful for those who have neither seen nor had the chance to see these diseases in the field or clinics. Such diseases are important not only in the tropics, but may be encountered in many countries in subtropical and temperate zones. - Features more than 100 images of lesions and laboratory findings of major skin diseases and diseases with skin manifestations that are prevalent in tropical areas - Includes clinical-case quizzes for self-directed learning - Covers laboratory diagnosis, clinical presentations, and the summary of all important facts about the disease, including their etiology

Part 1

Clinical Presentations, Laboratory Diagnosis and Disease Summaries

Outline

Clinical Quiz No. 1

Clinical Quiz No. 2

Clinical Quiz No. 3

Clinical Quiz No. 4

Clinical Quiz No. 5

Clinical Quiz No. 6

Clinical Quiz No. 7

Clinical Quiz No. 8

Clinical Quiz No. 9

Clinical Quiz No. 10

Clinical Quiz No. 11

Clinical Quiz No. 12

Clinical Quiz No. 13

Clinical Quiz No. 14

Clinical Quiz No. 15

Clinical Quiz No. 16

Clinical Quiz No. 17

Clinical Quiz No. 1

Abstract

Dermatophilosis (Streptothricosis) is an acute or chronic bacterial infection of the epidermis affecting animals and human. It is characterized by an exudative dermatitis with heavy scab formation and causes significant economic loss especially in cattle in tropical areas. Etiology: Dermatophilus congolensis, a gram-positive facultative anaerobic actinomycete bacterium which is spread by contact with infected animals, via contaminated environmental objects, and probably ticks. The disease is diagnosed by demonstrating branching gram-positive filaments in scabs; or isolating the organism in blood agar containing selective antibiotics and increased carbon dioxide tension. The disease is treated by topical (sulfur lime) or systemic antibiotics (gentamycin or penicillin G or tetracycline) and prevention can be achieved by managing ectoparasites and isolating or culling of infected animals.

Keywords

Dermatophilosis; streptothricosis; dermatitis; scab; Dermatophilus congolensis; actinomycete bacterium

What is your diagnosis?

A chronic skin infection in a zebu cow showing exudative dermatitis with heavy scab on the head, neck, and back. Note the enlargement of the superficial lymph nodes. Usually there is little effect on general health of the animal. Early stages show raised clusters of hairs tangled jointly as a wetted paintbrush (typical lesions). When these lesions merge, crusts (scab) are formed which develop to become wart-like lesions ranging from 0.5 to 2 cm in diameter.

Laboratory Diagnosis

Specimen

• Scabs (crusts, scales)

• Impression smears of the underneath lesions or biopsy.

Laboratory Tests and Findings

1. Direct detection by microscopic examination (Giemsa or gram stain—see Appendix for details of methods):

Gram-positive branching filaments with “train track” form or hyphae-like chains.

2. Culture

a. Fresh uncontaminated scabs or scab emulsions are streaked out directly onto culture media.

b. Blood agar containing 1000 units/mL of polymyxin B is an effective way to prevent overgrowth by contaminants. Plates are incubated at 37°C under 10% CO₂ for 2–5 days.

Growth of gray hemolytic colonies that become rough golden with age (Courtesy of doctors: Covarrubias, A.C., Zaragoza, C.S., Bucio, A.M., Aparicio, E.D., Olivares, R.A.C., 2015. CENID Microbiología Instituto Nacional de Investigaciones Forestales Agrícolas y Pecuarias, Mexico).

3. Indirect microscopic examination of grown culture (gram stain):

Branching filaments that break up into packets of coccoid cells. Tramcar line-like hyphae can be seen as well.

Diagnosis: Dermatophilosis (Streptothricosis, Rain Scald)

Answer and Disease Summary

Etiology

Dermatophilus congolensis

• A gram-positive facultative anaerobic actinomycete bacterium.

• It has two morphologic forms:

• Filamentous hyphae (tramcar line-like) and

• Motile zoospores.

• It grows on sheep-blood enriched agarose media when incubated at 37°C, under a 5–10% CO₂ for 2–4 days as small hemolytic gray-yellow colonies.

• Colonies become rough golden with age to enable isolation of the organism from a contaminated source, antifungal (nystatin) and antibacte...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Introduction
• Part 1: Clinical Presentations, Laboratory Diagnosis and Disease Summaries
• Appendix
• Further Reading
• Index