Causes of SORP (suboptimal reproductive performance) (4)
- Anoestrus/low ovulation rate
- Fertilisation failure/low conception rate – male infertility/unsoundness, inappropriate ewe:ram ratio, unsuitable environment
- Embryonic loss/early foetal death – severe undernutrition, low protein status (scab/fluke), persistent stress, Se/I deficiency, toxoplasmosis, border disease
- Late foetal loss – abortion, pregnancy toxaemia
Causes of poor ram fertility
- Testicular degeneration (testicle small compared to epididymis) /hypoplasia (everything is small)
- Epididymitis
- Traumatic injury to scrotal contents (orchitis)
Epididymitis
- Causes (2)
- CS (5)
- Dx (3)
- Tx
- Px
- UK: Gram negative pleomorphic bacteria (Actinobacillus seminis, Haemophilus somnus, Histophilus ovis) – ascending urogenital infection
- Overseas: Brucella ovis – infection across mucous membrane → bacteraemia → localization in epididymis
CS:
- Firm nodules in epididymis; testicular atrophy
- Pain
- Swelling
- Lameness
- inappetance during acute infection
Dx:
- Palpable lesions
- Leukocytes in semen
- Bacterial culture of semen
Tx: cull
Px: Control in problem flocks – keep ram lambs in small groups; avoid confinement and unhygienic conditions
Testicular hypoplasia/degeneration (2)
- Hypoplasia – usually inherited
* Degeneration/atrophy – secondary to e.g. systemic disease, inflammation of scrotum high environmental temperatures
Orchitis
- cause
- CS (4)
- Tx (2)
- trauma or infection (e.g. A. pyogenes, Brucella ovis)
CS:
- unilateral – heat/pain/swelling
- reduced testicular mobility
- induration
- degeneration of contralateral testicle
Tx:
- systemic antibiotics
- hemicastration
Aims of sheep reproduction (2)
- Normal gestation length ~147 days (142-150)
* Aiming at <2% abortion
Infectious causes of abortion
- Bacteria (5)
- Protozoan (2)
- Rickettsia (2)
- Viral (1)
- Fungae (2)
Bacterial:
- Chlamydophila abortus (enzootic abortion)
- Campylobacter (vibrosis)
- Salmonella
- Listeria monocytogens
- Leptospira interrogans
Protozoan:
- Toxoplasma gondii
- Neospora caninum
Rickettsia:
- Ehrlichia phagocytophilia (tick borne fever)
- coxiella burnetii (Q fever)
Viral:
- border disease
Fungae
- Aspergillosis fumigatus
- calviceps purpurea
Non -infectious causes of abortion
- Inadequate nutrition
- Pregnancy toxaemia
- Stress/poor handling
- Vaccination
- Transport
- Dog worry
- Pasteurellosis
- Chronic fluke
Investigation of abortion (7)
- history, assessment of environment & CS
- lab investigation of whole foetus/placenta
– Piece of placenta (cotyledon + membranes)
– Foetal stomach contents (aseptically collected)
– Foetal thoracic/peritoneal fluids
– Fresh spleen
– Fixed (formalin) cotyledon, foetal liver, brain etc.
Measurements when abortion is confirmed
- Isolation and marking of aborted ewes
- Prompt disposal of products of abortion
- Strict biocontainment
- Strict hygienic precautions
- Reduced stocking density
Chlamydial abortion
- when
- CS (2)
- Dx (6)
- last 3 weeks of pregnancy
- apparently healthy – may stop eating, reddish vaginal discharge
- Lambs freshly dead or alive (but often weak and unable to suckle)
Dx:
- Placentitis caused by intracellular replicative phase of bacteria
– Discoloration/necrosis of cotyledons
– Oedema/rough thickening of intercotyledonary membranes
– Yellow/pink pus-like exudate
- Confirmation by demonstration of large numbers of chlamydial elementary bodies in Ziehl-Neelsen stained smears of placental tissue
- Paired serology – if no aborted material
Chlamydial abortion
- Transmission (3)
- Outcomes (3)
- Control (4)
Transmission:
– Aborted foetuses/placentae
– Vaginal discharges
– Live-born lambs
Outcomes:
- late pregnant/ non pregnant: no immune response, abortion in last 3 weeks of next pregnancy
- first half of pregnancy: abortion in last 3 weeks of same pregnancy
- immune: may shed chlamydia in following lambings, surviving lamb aborts during first pregnancy
Control:
• Isolate aborted ewes + surviving lambs
• Remove products of abortion and contaminated bedding
• Antibiotic treatment of whole flock or in-contact ewes (10mg/kg long-acting oxytetracycline)
• Vaccination: Live attenuated vaccines, Need on-going challenge to keep up immunity
Toxoplasmosis
- epidemiology
- CS
- Toxoplasma gondii
- Intestinal parasite of cats – faecal shedding of oocysts for 8 days when first infected, then immune
- IMH: sheep, birds, mice: tissue cysts in brain and muscle
- Minimum infective dose for pregnant ewe ~200 oocysts
- Oocysts survive up to 2 years in cool & moist environment
- isolated from ram semen
CS:
– Early pregnancy – embryonic death/ resorption (barren ewes)
– Mid-pregnancy – foetal death (mummification); foetal growth retardation
– Late pregnancy – freshly dead lambs; weak live lambs
Toxoplasmosis
- Dx (4)
- Control (6)
Dx:
– Placenta – hyperaemic cotyledons, with small white foci of necrosis and calcification; (intercotyledonary membranes normal)
– Lamb – subcutaneous oedema; fibrinous exudate in pleural & peritoneal cavities
– Histology – cotyledons, foetal brain, heart, liver, lung, spleen
– Serology – foetal pleural/peritoneal fluid (IFAT)
Control:
• Rodent control
• Keep feed stores secure from cats
• Limit cat breeding-aim for a stable healthy cat population
• Sulphonamides (e.g. sulphadiazine) – no longer licensed for sheep in UK – Same with Monensin
• Decoquinate (Deccox 6%™) – medicate feed to give 2mg/kg body weight daily; last 14 weeks of pregnancy (if practical!)
• Vaccination (Toxovax™) – live vaccine; single dose at least 3 weeks before mating
Campylobacteriosis
- causes (2)
- pathogenesis
- Cs (3)
- Campylobacter fetus subsp. fetus
- Campylobacter jejuni
Infection of pregnant ewes → bacteraemia → localization in placenta & foetus → acute necrotic inflammatory response → abortion 7-25 days after infection
CS:
- Abortion in last 6 weeks of pregnancy
- Placenta – inflamed, oedematous, may be covered by thick yellow-white exudate
- Aborted foetuses – usually fresh, may contain serosanguinous exudate in body cavities
Campylobacteriosis
- Dx (2)
- Tx/Px (5)
Dx:
- Smears from placenta and/or foetal stomach contents – Ziehl-Neelsen or Gram stain – small, paired, comma-shaped bacteria (“seagull”)
- Bacterial culture of stomach contents to confirm
Tx/Px:
- Immediate isolation of aborted ewes – treat with broad spectrum antibiotic
- Safe disposal of products of abortion
- Reduce environmental challenge – e.g. move fields, reduce stocking density
- Aborted ewes immune; some become carriers
- Vaccination widely used in e.g. USA & New Zealand (not available in UK)
Salmonellosis
- causes: UK (3)/ overseas (2)
- sources
- CS: motevideo (2)/ dublin (2)
- Tx
UK:
• Salmonella enterica serotype Montevideo
• Salmonella enterica serotype typhimurium
• Salmonella enterica serotype Dublin
Overseas
• Salmonella enterica serotype abortus ovis
• Salmonella enterica serotype Brandenburg
Sources of infection: contaminated feed/ watercourses, carrier animals, wild birds – difficult to avoid
CS:
Salmonella Montevideo
- SE Scotland
- Abortions throughout second half of pregnancy
Salmonella Dublin
- Infection via carrier cattle
- Systemic illness & diarrhoea more frequent in ewes
Tx:
-S. montevideo – whole flock treatment with long acting oxytetracycline
Border disease
- agent
- CS (3)
- Dx (2)
- Control
- Pestivirus
CS:
- < Day 60 – “hairy shaker” lambs; persistently infected
- Days 60-85 – congenital defects – brain, musculoskeletal
- > Day 85 – foetal immunity; normal lambs
Dx: (difficult)
- Pestivirus antigen in foetal/lamb blood & tissues
- Serology – ewes; aborted foetus
Control:
- Identify and cull persistently infected animals
Schmallenberg virus
- agent
- foetal abnormalities (3)
- spread (2)
- Px
- Orthobunya virus
- Still birth
Foetal abnormalities:
– Arthrogryposis
– Twisted neck or spine
– Short lower jaw
- Vector borne disease (midges)
- Viraemia 2-5 days
- Vaccination (Bovilis SBV – MSD)
