Infectious: bacteria, viruses, protozoa, algae, fungi, prions
Parasitic: Parasites (endoparasites, exoparasites)
Metabolic: failure of the animal to fully overcome changes in its environment, due to insufficient nutrition
Pasteurellosis is of considerable economic importance to the sheep industry causing:
Septicaemia in young lambs
Pneumonia in older sheep
Mastitis in ewes
Infectious agents: Mannheimia haemolytica, Bibersteinia trehalosi and Pasteurella multocida
These bacteria are found normally in the throat but multiply when the animal is under stress and immunity is suppressed.
Sudden onset of depression
Lethargy and inappetence
Affected sheep typically become separated from the remainder of the group
Increased breathing rate with an abdominal effort and fever (>40.5°C)
In some situations, the animal is found dead.
Sheep with pasteurellosis separated from the group, not eating and very dull with ears down.
Sheep with acute pasteurellosis is depressed, lethargic and ears are down.
At necropsy, the lungs are heavy, oedematous, and purple-red with ecchymotic haemorrhages following death from Mannheimia haemolytica infection
Appropriate antibiotic therapy: Oxytetracycline is often prescribed for pasteurellosis in sheep but seek veterinary advice.
Anti-inflammatory treatment is also advised.
Minimize stress and reduce the circulating levels of bacteria
For housed sheep ensure the ventilation and drainage are adequate and stocking levels are appropriate
Address the nutritional requirements correctly and ensure adequate surveillance and treatment of parasites
Incoming sheep and sheep showing signs of clinical pasteurellosis should be effectively isolated from the rest of the flock according to the flock health plan.
Vaccination can be used to protect all susceptible sheep from clinical disease
Etiology: Infectious agent: Listeria monocytogenes, a bacterium that lives in a plant-soil environment The nervous form of listeriosis is primarily a winter-spring disease, most commonly but not exclusively, associated with silage feeding.
Silage with obvious mould growth suggests poor storage conditions
Big bales of grass silage in ring feeders may not be eaten for up to 10–14 days, allowing rapid bacterial multiplication
Listeriosis is found classically in sheep and goats fed poorly conserved silage and it affects all ages and both sexes, sometimes as an epidemic, in feedlot small ruminants
A)Nervous form: Listeric encephalitis.
General symptoms: depression, loss of appetite, fever
Neurological symptoms: lack of coordination, salivation, facial paralysis, and circling. Disease is more common in animals 1 to 3 years of age than it is in older animals. The onset of the encephalitic form is usually very fast and causes death in 24 to 48 hours after symptoms appear
B) Abortion form: shows no other symptoms besides abortion and can only be diagnosed by laboratory analysis
PCR: PCR-based methods are now being used increasingly in mastitis diagnostics with good reliability as a complement to bacterial culture
B)Sub-clinical mastitis. It is defined as the presence of inflammation with a normal appearing mammary gland and visibly normal milk.
Different detection methods exist but they are not always used in small ruminants.
Treatment: Appropriate antibiotic administration based on microbiological exams and antibiogram, anti-inflammatory medicines.
The direct effects (including bacterial transport, cross-contamination and impacts) might account for about 10% of new infections on most farms.
Indirect effects (including effects on the health of the teat canal, teat tissues and skin) might account for another 10% in an average herd.
Clostridial Diseases (B)
Etiology: Clostridium spp
The most common clostridial diseases are:
Malignant Oedema (Bighead)
Sporadic cases of clostridial disease may occur in the flock in those lambs which have received zero or inadequate specific antibody in colostrum due to various factors:
Treatment: With the exceptions of blackleg and bighead, there are no effective treatments for the clostridial diseases
There are well-established vaccination protocols using toxoid vaccines which prevent all common clostridial diseases
It is a very important infectious disease in the Mediterranean basin, where it is usually caused by Brucella spp (bacteria), mainly Br. Melitensis or Br. Ovis.
Brucella spp. affect, in small ruminants, mainly the pregnant uterus of female.
It causes abortions, stillbirths or birth of weak lambs. Brucella abortions occur late in gestation, following placentitis with edema and necrosis of the. Fetuses aborted following brucellosis can be alive, stillbirths or even autolyzed or mummified.
Aborted foetus with necrotic placenta (photo albetar portalveterinaria, https://www.angoras.co.za/)
Brucella spp can reside in males’ testis and epididymis, either causing profound epididymitis of, being subclinical, infect the females the carrier hosts, while the male becomes subfertile.
Brucellosis in a ram: Scrotum oedema
On a flock base, Brucellosis causes subfertility / infertility.
There is no proper treatment for animals that are infected.
The only way to deal with the disease is to vaccinate, slaughter or combine both in order to eradicate it
Brucellosis is a serious zoonosis, that can cause severe damage to people who get in contact with affected animals (mainly during animal labours, milking or vaccinating against brucellosis).
Enzootic abortion is caused by Chlamydia abortus, and leads to late-term abortion. It may appear in an outbreak or an enzootic form.
Infection is usually through the digestive tract (mouth), originating from infected placentae. Ewes abort only once, but they may remain carriers. Ewes infected before 5 or 6 weeks of gestation abort in late gestation, but ewes infected after 5 or 6 weeks of gestation abort in the subsequent pregnancy.
Diagnosis: Late-term abortion, followed by tests performed at the aborted material
The embryo is usually aborted while
-Isolation of aborted animals, destruction of aborted material, disinfection of the site of abortion
-Inserting replacement animals from chlamydia-free sources
-Adopting good management practices to prevent introduction of chlamydia to the herd
-If Enzootic Abortion outbreaks within a herd, antibiotics (oxytetracycline) might limit the number of abortions.