Ovine Pathogens

Question 1

Bluetongue pathology findings

Answer 1

white streaks in the skeletal muscles and endothelial hemorrhage at the base of the pulmonary artery, as well as ecchymotic hemorrhages in the lymph nodes and spleen. Underlying lesions are vasculitis, and the lesions are multisystemic.

Causes abortion, fetal-mummification, stillbirth, and congenital brain malformation.

Transmitted by biting midges and vaccine available

Question 2

Border Disease

Answer 2

“hairy-shakers”

Caused by infection of fetus in early pregnancy with a pestivirus (Flaviviridae). Related to Classical Swine Fever and BVD

Surviving lambs are persistently viremic

Abortion may occur at any stage

No effective treatment, serology on dams of affected lambs,

Problem in nieve herds

Question 3

Brucella ovis in rams

Answer 3

Infertility and epididymitis

Question 4

Champylobacter

Answer 4

most common cause of abortion in sheep in North America

Venereal, control with AI and vaccination

Question 5

Clostridium novyi Type A

Answer 5

“Big head” treat with wound debridement and penicillin

Found in soil so culling and isolation unnecessary. Enters through wounds obtained during head-butting activities. Fatal if untreated.

Question 6

Copper deficiency

Answer 6

Causes enzootic ataxia in goats and sheep. Can be primary (low intake) or secondary (factors inhibiting absorption and promoting excretion, ex. high sulfur, iron, selenium). Deficiency can cause microcytic anemia, decreased production, fading hair, heart failure, infertility, swollen joints, gastric ulcers, and diarrhea. Two neurologic diseases specific to copper deficiency are enzootic ataxia (seen in lambs 1 to 2 months old) and swayback (seen congenitally or in very young lambs and kids). Clinical signs of progressive ascending paralysis nd incoordination, muscle atrophy, and weakness. Copper deficiency leads to less myelin formation and to demyelination.

Question 7

Culicoides gnat

Answer 7

bluetongue vector

Question 8

Dermatophilus congolensis

Answer 8

Actinomycete that primarily affects the dorsal surface of animals. Clinically, crusting lesions will form which are easy to pull off, and many people describe them as a paintbrush lesion. In sheep, this disease may be known a strawberry footrot when the claws are affected. Remove sheep from rain.

Question 9

Dichelobacter nodesus

Answer 9

Primary pathogen in footrot

Question 10

Estrus duration

Answer 10

1.5-2 days, ovulations occurs about 24 hours after onset of estrus

Question 11

External caseous lymphadenitis

Answer 11

Caseous lymphadenitis (CL) is a chronic, contagious disease caused by the bacterium Corynebacterium pseudotuberculosis.

gram-positive, facultative, intracellular coccobacillus

abscesses in the region of peripheral lymph nodes

More common form in goats

Question 12

Footrot

Answer 12

Primary Dichelobacter nodesus Secondary Fusobacterium necrophorum

Question 13

Fusobacterium necrophorum

Answer 13

secondary infection in footrot

Question 14

Gangrenous mastitis

Answer 14

Caused by Mannheimia hemolytica and Staphylococcus aureus and occurs sporadically during the first 3 months of lactation. It if generally associated with poor milk supply relate to ewe undernutrition and over vigorous suckling lambs. Prognosis is grave. Control measures include ensuring ewes are well fed. Concentrated should be supplied to ewes and lambs when pasture is poor. No ewe should be expected to rear triples. Teat lesions should be identified and treated with topical antibiotics.

Question 15

Gid (coenurosis)

Answer 15

Caused by a tapeworm Coenurus cerebralis which is the larval form of Taenia multiceps. The sheep is an intermediate host and the larvae invades the sheep’s central nervous system, forming a cyst in the brain

Question 16

Grass staggers

Answer 16

results when plants of the genera Phalaris (Canary grasses), Lolium, Cynodon, or Paspalum are ingested. Some, like Canary grass, accumulate toxic alkaloids, while others harbor fungi with toxins. Canary grasses can cause either acute death or grass staggers. Most sheep affected by Canary grass staggers will slowly recover if removed from the offending pasture. Grass staggers is also the name of hypomagnesemia in sheep which can develop in sheep grazing lush grass pastures. It is easy to get this condition confused with the intoxication presented in this question due to the similar title of the clinical condition. Symptoms of hypomagnesemia include restlessness, staggers, an over-alert appearance, being excitable, and in some cases, aggressiveness. In severe cases, animals may fall down and go into convulsions or just die without warning.

Question 17

Hydroanecephaly

Answer 17

in lamb - bluetongue infection in early gestation

Question 18

Internal caseous lymphadenitis

Answer 18

thorax and abdomen - more common form in sheep

Question 19

Johne’s disease (Mycobacterium avium ssp. paratuberculosis)

Answer 19

acid-fast rods tell tale sign of Johne’s. Typically a disease of chronic wasting, affecting animals 2 years and older.

Question 20

Mannheimia haemolytica

Answer 20

Formerly called Pasteurella hemolytica, most common infectious bacterial disease of sheep and goats. “Blue bag” and enzoonotic pneumonia which is a hemorrhagic bronchopneumonia of young lambs and their dams. Clinical signs: fever, depression, mucopurulent nasal discharge, coughing, pulmonary crackles and wheezes, and tachypnea. Fibrinopurulent pleuropneumonia.

Question 21

Melophagus ovinus

Answer 21

“sheep ked” one of the most widely distributed and important external parasites of sheep.

Wingless dopterans. Entire lifecycle is spent on the host.

Adult is 7mm long, brown/red, armed with stout claws.

Need to remove sheep from infected areas - only effective treatment

Question 22

Mycoplasma mycoides ssp. mycoides

Answer 22

causes a number of conditions including pleuropneumonia, mastitis, polyarthritis, and meningitis, but is seen mainly in goats.

Question 23

Mycoplasma ovipneumoniae

Answer 23

pneumonia in sheep

upper respiratory tract

predispose to secondary infection with Pasteurella and Mannheimia

Question 24

Oestrus ovis

Answer 24

treat with ivermectin Adult flies deposit larvae around animals nostrils, larvae migrate up the nasal passages into the turbinates and sinuses. With time and multiplication of the larvae, hypersensitivity develops -> clinical signs of discharge and face rubbing and shaking. Secondary bacterial infection can occur. Eosinophils and mast cells seen in the discharge.

Question 25

Ovine Progressive Pneumonia

Answer 25

Maesi-Visna - caused by a retrovirus closely related to CAEV (Caprine arthritis and encephalitis virus), with increasing wasting and respiratory distress. Secondary bacterial infections can occur, leading to coughing, bronchial exudate, depression, and fever. Indurative mastitis (hardbag) may occur. In the encephalitic form, ataxia, muscle tremors, or circling may occur and progress to paresis and eventually paralysis. Diagnosis may be confirmed in live animals via agar gel immunodiffusion of ELISA testing. No vaccine or treatment is effective, the disease is controlled by serologic testing and removal of positive animals. Re-test annually due to long incubation period and fed lambs colostrum from seronegative ewes.

Question 26

Ovine/Caprine Nasal Adenocarcinoma Virus (ONAV/CNAV)

Answer 26

tumor is not metastatic but locally expansive and destructive.

Question 27

Pasteulla multocida

Answer 27

pneumonia and septicemia in sheep and goats

Question 28

Ulcerative Posthitis

Answer 28

“pizzle rot” in male sheep - corynebacterium renale in ulcers on the sheath

Question 29

Veratrum californicum

Answer 29

Associated with the cyclops condition in sheep