Abortion and Perinatal Loss in Sheep and Goats
Lecturer: Dr. Donal O'Toole
Abortion and perinatal loss in sheep and goats is both simpler and more complex than the conditions in cattle. Simpler, as the number of infectious agents involved is fewer. Some (but not all) can be vaccinated for. More complex, since at least three of the important agents are transmissible to people - they are zoonotic. If you have to deal with an abortion storm in sheep or goats, assume that it may be one of the zoonotic agents. Protect yourself (gloves and calving gown; soap; disinfectant; bury or burn fetal membranes and fetuses). Several of the agents cause illness, including abortion, in pregnant women. Pregnant women and people with immuocompromising diseases should avoid involvement with lambing ewes or kidding goats. They should not handle contaminated clothing from those who worked with lambing ewes and newborn lambs.
Abortion rates above 5% should trigger a suspicion that something infectious is involved. Below I list some of the important ones for our area. Other agents can be involved elsewhere in the USA. These include Cache Valley and bluetongue viruses, sarcocystosis, and iodine deficiency (goiter).
This disease is correctly called campylobacteriosis. The old name for the organism, Vibrio, continues to be widely used. This is the most important single diagnosed cause of abortion in Wyoming. Abortion rates may be in the 10 - 20% percent range. They can reach 80% in completely naive flocks, particularly when the tally includes perinatal loss due to lambs born alive but then die. Infected ewes generally recover following abortion and are solidly immune to reinfection. Some ewes remain persistently infected and continue to shed bacteria in feces. This is one reason why pregnant ewes should not be fed on the ground (two other abortifacient agents, Salmonellla and Chlamydophila, are also shed in feces and can be acquired from the ground). Some aborting ewes die of complications, such as an infected uterus (metritis), fetal retention, or peritonitis. Stillbirths and weak lambs are common. Vibrio abortion in sheep is not venereal (unlike the related Campylobacter sp. disease in cattle). Ewes are infected by ingestion of the organism. Since the agent can be found in wildlife, including birds, some producers are preoccupied with this as a potential source. Failure to vaccinate, and introduction of one or more infected ewes, is the most common scenario prior to an abortion storm. We only see the disease in flocks where a vibrio vaccine is not used.
Antibiotics: YES (make sure the laboratory isolate is sensitive to what you use).
Enzootic abortion of ewes (EAE) is characterized by abortions, stillbirths and weak lambs. When EAE first appears in a flock, abortion rates run from twenty-five (25%) to sixty (60%) percent. Once the disease becomes established, losses in subsequent years drop to 1 - 5%. Clinical evidence and history of a low incidence of EAE in the Midwest suggest that the disease is endemic there. In the West, isolated range flocks become highly susceptible when the disease is introduced. Likewise, when ewes from clean Western flocks are introduced to endemic areas in the Midwest, high abortion rates may occur. Ewe lambs are the most susceptible age group when exposed on endemic farms. The organism can also cause pneumonia in young lambs. Initially, it was thought that the disease was spread only through contact with infected fetuses, placentas or vaginal discharges. However, clinical evidence indicates that the disease may be spread by infected sheep constantly shedding agent in feces or from lungs - so it replicates in cells lining the gut, and also cells in the respiratory tract. The organism enters a non-pregnant ewe and lays dormant until the animal conceives. The organism does not initiate an immune response during the dormant stage. During the infective stage, the ewe develops an immune response that clears the organism from her system. The Chlamydophila agent that causes abortion is distinct from a related agent that causes conjunctivitis/polyarthritis in lambs. The vaccine for the conjunctivitis agent does NOT protect against the abortion agent.
Extension piece by Dr. Susan Rodger at Moredun Research Institute on EAE
Border disease was first reported in 1959 along the English/Welsh border, hence the name. You may sometimes hear it called ‘hairy-shaker’ or ‘fuzzy-lamb’ disease. The disease it causes is similar to that of BVDV in cattle. Indeed, some strains of BVDV cause a border disease-like syndrome. It causes minimal effects in the dam. If it infects young post-natal lambs, the outcome can be serious. As with BVD, the clinical outcome depend on the time at which fetal lambs are infected in gestation. Infection before mid-gestation (~80 days) results in abortion or the birth of persistently infected lambs ("hairy shakers"). These lambs are hairy because the virus infects and damages cells of the primary hair follicles; they shake because of damage to myelin-forming cells in the CNS. Myelin's normal function is to form an insulation-like wrapping around nerve fibers in the central nervous system; when the myelin is reduced, nerves can still talk together, but less well. The clinical effect is similar to multiple sclerosis in people. After ~80 days, when the fetus can mount an immunological response, the outcome varies from abortion, stillbirth, weak lamb, to nothing at all. This is important since lambs aborted before 80 days will still be infected; those born after ~ 80 days have no detectable virus. This makes confirmation of border disease abortions a problem at the laboratory end. As in BVD, some lambs infected early in gestation survive and remain infected for life. They are a constant source of infection. Sheep-to-sheep contact is the principal way in which BDV is spread. The most potent sources of virus are PI sheep. Flocks with no previous exposure to the virus are particularly vulnerable. Purchase of PI replacement ewes is the commonest way of introducing infection. These animals constantly shed low levels of virus from the skin and excrete it in feces and urine. The highest concentration of virus, however, is in nasal secretions and saliva. The spread of virus in a susceptible flock exposed to one or more persistent excretor animals will depend on contact between sheep. Housing during early pregnancy has been shown to result in explosive outbreaks of border disease. To avoid the risk of infection with BVDV, pregnant sheep should not be mixed with cattle.
VACCINE: NO - there is such variability among pestiviruses that BVD vaccines are unlikely to protect from BDV
4. Toxoplasmosis in sheep (cause: protozoal agent belonging to the coccidia family; Toxoplasma gondii)
Toxoplasmosis is a common causes of abortion in Europe (27% of all diagnosed causes of abortion in sheep in UK, 1995 - 2003) and the Midwest. We have rarely seen it in Wyoming. I assume the main reason is that there is less opportunity for cats, which shed the agent in their feces, to have contact with range flocks. Toxoplasma abortion in ewes follows ingestion of feed or water which has been contaminated with oocyst-laden cat feces. The infection is maintained in cats, who often acquire it from infected rodents. Toxoplasmosis generally does not cause clinical symptoms or detrimental effects in open, healthy ewes. The result of toxoplasmosis in pregnant ewes varies with the age of the fetuses when the ewe is infected. Infection in the first two months of gestation results in embryonic death and resorption. Infection in mid gestation results in abortion and infection. Infection in the late gestation results in abortions, stillbirths, mummies or weak lambs. Flock abortion losses attributable to T. gondii can involve from 5% to 50% of the ewe flock. Typical losses are 15 - 20% of the lamp crop. T. gondii can infect people and cause a mild flu-like illness - a colleague of mine developed this when I was in practice in Ireland. In pregnant women and immunocompromised individuals infection can be more serious and on rare occasions be fatal
Ewes that become infected develop solid immunity. There has been some suggestion that infected ewes abort repeatedly. The institute that has done much of the pioneering work on this disease (the Moredun Research Institute in Scotland) has found little evidence to support this. Ewes that abort should be retained in the flock since they are solidly immune.
VACCINE: NO - not in US. There is a vaccine made by Intervet called ToxovaxTM. It is licensed for use in New Zealand and several European countries. This live vaccine should not be used in pregnant ewes, and should not be administered by pregnant women or immunocompromised people. It is unlikely to be licensed in the US anytime soon.
IONOPHORES: YES for control (decoquinate. dose is x4 FDA recommended dose)
Q fever is caused by the rickettsial agent Coxiella burnetii. It is more common as a cause of abortion in goats than sheep. We have seen it in Wyoming, mostly in goats. Human cases of Q fever are associated with exposure to abortions in sheep and goats, drinking unpasteurized goat milk and eating soft cheeses, and contact with clinically healthy infected sheep and goats. Most human infections with C. burnetii are asymptomatic or result in mild transient flu-like illness. Serious infections result in permanent cardiac injury; fortunately this is rare. The number of organisms shed from aborting ewes and goats is enormous. People are readily infected by aerosol. The agent persists an extended time in the environment. Ticks play a role in transmitting the disease in nature. There is a good recent review of Q fever in JAVMA.
ANTIBIOTICS: YES - long-acting antibiotics such as tetracycline in water reduce shedding of the organism but there have been no studies to determine whether they can clear infection.
Tularemia as a cause of abortion is now mostly a historical disease in Wyoming and adjacent states (SD; MT; ID). It continues to occur in areas and at times when ticks (esp. the Rocky Mountain wood tick) and cottontail populations are abundant. In the past it was the basis for large outbreaks of abortion and illness in 1 - 2 month old lambs in range flocks. We saw outbreaks of this in 1997 and 2007. In one episode a producer lost almost 50% of his lamb crop. Typically this occurs a) in March - May; b) shortly after sheep are put onto heavily tick-infested pastures; c) when there has recently been a large die-off among lagomorphs, esp. cottontails. Ewes may be ill, but few die. Outbreaks in lambs is manifest as stiffness, big lymph nodes (usually on the shoulders, due to the feeding location of ticks), and high fever. The typical rabbit fever cycle in our area is between ticks and rabbits, with spillover to sheep and people. You can be infected from handling carcasses, fluids or ticks on sheep. The mortality with tularemia in people is relatively low but you don't want to become a CDC statistic. As in any situation where you handle disease material and become sick, tell your primary care physician so she or he can factor it in.
ANTIBIOTICS: YES - tetracycline slows losses. Move the sheep to pastures with fewer ticks, if available. Treat all sheep for ticks using topical acaricides.
I mention this not because it is common in the US, but since it is one of the nastier form of brucellosis you can get from animals. It is diagnosed periodically in some states (California, Florida, Texas). We have not seen it in Wyoming (when we were cleaning out a storage room some years ago, we found a dried up vial labeled as B. melitensis. The vial looked old, and out of curiosity we tried to culture it. To our astonishment, it came up on culture. This is a reflection of the relative hardiness of the organism). It causes abortion in late term does, and can be shed in milk.
This venereal infection of sheep is due to the bacterium Brucella ovis. It occurs n Wyoming flocks. Testing for it is problematical since the official USDA test gives rise to false positive results, to the consternation of woolgrowers. Personnel at National Veterinary Services Laboratories and the state laboratories have worked to refine the B ovis ELISA test.
This organism likes to infect the male reproductive system, specifically the epididymis. This is the portion of the male reproductive tract where spermatozoa are stored before they march to their destiny. As with other members of the tribe, B. ovis causes chronic infections. Once infected, rams tend to remain so for life. The epididymis (unilaterally or bilaterally) become inflamed and swollen. One way to confirm a laboratory diagnosis is to palpate the epididymis (especially the anatomical portion called the tail). Epididymitis, if severe enough, blocks semen from passing from the testicles to the penis. In some infected rams, the testicles become atrophic. The main effect is reduced or lost fertility. Infection in flocks is associated with reduction in the lambing percentage of up to 30% in newly exposed flocks, and 15 - 20% in flocks where it is endemic. Unlike B. abortus, the sheep agent does not infect people. Generally, fertility is not compromised until the proportion of rams with chronic, palpable lesions exceeds 10 - 20%.
Economic wastage due to:
1. Extended lambing period
When infected rams of low fertility serve ewes in heat, the chances of conception is reduced. Many ewes return to service 17 days later. In some affected flocks, more than half return to service. If rams are removed after six weeks, many ewes may not be pregnant.
2. Reduced lamb production
When a high percentage of clinically affected rams is used, the lambing percentage may be reduced. Replacing rams every two or three years or purchasing rams from untested ram supplier flocks or culls from a sale yard can introduce disease and result in a high prevalence of infected rams.
3. High culling rate of rams
Rams become infected as young as 4 months. Transmission occurs mainly from ram to ewe to ram - a typical venereal (STD) infection. A second method of transmission is sodomy, which is common in young rams, unless they happen to be from Utah, where this sort of activity is frowned upon and therefore cannot exist. Infection of ewes is generally short-lived. Persistently infected ewes do not play a big role in maintaining disease in flocks. Once rams are chronically infected, excretion of bacteria in semen persists essentially indefinitely.
There are several blood tests for this condition. The official ELISA test used by many diagnostic laboratories has a problem: it gives rise to false positive reactions. Animals become blood test positive (= seroconversion) 10 - 66 days after infection. Semen culture can be used and is generally positive 5 - 10 weeks post-infection, but most producers prefer the blood test since that matrix is more accessible. Lesions are palpable from 9 weeks on post-infection. A few challenged rams never develop evidence of infection, whereas others develop serological evidence only. The former rams recover and are said to have had ’abortive’ infections. Serological reactions decline in recovered animals over a period of 4 - 5 months. In animals that remain chronically infected, serological responses remain relatively constant.
Deterioration in semen quality occurs early in the disease. Semen contains many leucocytes (the main ingredient of pus). In acute stages of the disease, there is edema and inflammation of the epididymis and tunics, palpable as a general swelling, and loss of definition of the scrotal contents. The typical lesion is enlargement of one or both the epididymes, usually in the part called the tail, which becomes firm due to scar tissue formation (fibrosis). The epididymis may be ~3 times normal size. There is no inflammation of the testicles (orchitis) and initially the testes feel normal. Later degeneration and atrophy may lead to a decline in size and firmness of the testes. Less commonly, enlargement and hardening may involve more of the epididymis, or the head only or may not involve the epididymis at all, being restricted to one or more of the accessory sex glands.
The presence in a flock of chronic epididymal lesions in more than 5% of rams suggests brucellosis. Lesions of chronic epididymitis must be differentiated from those caused by trauma and by other bacteria.
It is possible to intensively test for and eliminate this in flocks. Some states such as South Dakota run voluntary B. ovis eradication programs, and go to some lengths to keep the disease out of the state. A negative B ovis test is required for ram sales in Wyoming.
Rams with low blood titers are frequently found to be uninfected and are probably recovering from abortive infections. Low titer positive animals with no palpable lesions be isolated from other rams and re-tested after 4 weeks. Persistently low titers warrant slaughter and detailed necropsy examination so that the status of the flock can be determined.In commercial flocks, brucellosis can be eradicated by isolating the existing, infected ram flock, purchasing replacement rams from accredited B. ovis free studs and keeping them at all times separate from old rams. Eradication from the older rams can be attempted by test and slaughter. There is a risk that the infected rams will gain access to the young rams and cause a breakdown, so the shorter the duration of the ’two flock’ system the better. In ram breeding flocks, a program of test and slaughter will successfully eradicate brucellosis, provided new cases are detected before they commence excretion of B. ovis organisms, which occurs as soon as 4 weeks post-infection. Serial testing should be performed every 3 weeks. All reactors should be culled. Older rams with lesions of epididymitis should be culled regardless of serological results - false negative results occur in some chronically infected animals. Infection of ewes is a potential a source of breakdown during eradication. This is rarely a problem of practical significance.
Vaccination has been used in New Zealand as a control measure, but it is not used in the US as far as I am aware. At time, Australian producers used a combination of a formalin-killed B ovis saline-in-oil emulsion and B abortus strain 19 vaccine. Equal efficacy of some B ovis vaccines when administered twice, 2 weeks apart, has been demonstrated.
Goiter means non-neoplastic, non-inflammatory enlargement of the thyroid gland. There are two major causes in our area: low iodine in the diet, and inherited forms. Goiter occurs in multiple species, but we most commonly see it in goats > sheep > cattle. Boer goats, a meat breed that grows fast, seems especially prone to goiter. It is a fairly common cause of perinatal death in kids, in my experience. Goats and other affected species have characteristic swellings (due to large thyroid glands) immediately behind the jaw as shown in the image below. The typical presentation is a weak, thinly haired newborn with a marked swelling immediately behind the angle of the jaw. Affected kids and lambs generally die. The diet should be analyzed for its iodine content and, if low, supplemental iodine fed.
This is the number one killer of lambs - many losses blamed on predation represent weak, dying and dead lambs that have been recycled by coyotes and foxes. When lambs are born, they have limited body fat and, when it is wet and cold, they develop hypothermia rapidly. Light lambs have a higher surface area and chill quickly. Normal body temperature for lambs is 99 - 102 F. Hypothermic lambs rapidly become recumbent and comatose. When we see these guys at necropsy, there are not much to see: sometimes there is early pneumonia and the lambs have lost their brown fat.
Moderate hypothermia (temperature >99°F) in a lamb less than 5 hours old. In most cases a lamb this young will still have some energy reserve and, therefore, glucose administration will not be necessary. The lamb should first be vigorously towel-dried and then given colostrum. If it can nurse, encourage it; if not, feed 2 ounces by stomach tube at two hour intervals. The lamb need not be warmed with more than a heat lamp in a draft-free claiming pen.
Severe hypothermia (temperature less than <99°F) in a lamb less than 5 hours old. The lamb should be dried and warmed - rapid warming important. This can be done by putting the lamb into warm (104 F) water or by using a warming box. If the lamb is flat out (approaching coma), it also needs glucose. This is best given using sterile technique and injecting a 20% glucose solution into the abdominal cavity. Once the lamb’s rectal temperature reaches the normal range (99°F). it should receive colostrum, as before.
For lambs that are older than 24 hr., hypothermia usually is a result of starvation. Without energy from milk lambs become hypoglycemic, hypothermic, then die. Treatment for these situations is similar to that used for the newborn, with the exception that older lambs need not receive colostrum. Milk replacer can be fed with a bottle or tube fed. As a guideline, these older lambs should receive 6-8 oz. of warm milk.
There are several major causes of diarrhea in nursing lambs. The most important are:
a. E. coli
E. coli scours are an opportunistic disease associated with dirty environmental conditions and poor sanitation. It generally occurs as a diarrhea problem in two to four-day-old lambs. Affected lambs salivate and have a cold mouth; thus the common name, "watery mouth." Dehydration, coma and death usually occur within 12-24 hours following onset of clinical signs of scours. Treatment of E. coli scours usually involves rehydrating lambs with oral, subcutaneous or intraperitoneal fluids and treatment with appropriate antibiotics. Prevention of E. coli scours in lambs should be an important goal for any flock. Lambing barn sanitation and creating a clean dry environment for newborn lambs are important for preventing outbreaks of E. coli scours.
b. Clostridium perfringens
As in calves, Clostridium perfringens is causes death in newborn and nursing lambs. One strain (Clostridium perfringens type C) affects the very young lambs (<2 weeks of age). They present with bloody diarrhea. It is often related to indigestion and predisposed by a sudden change in feed such as beginning creep feeding or an abrupt increase in milk supply. Treatment (antitoxin injected under skin) is usually unrewarding Vaccination of pregnant ewes 30 days before lambing is recommended as prevention. The other form is seen in older lambs and is the classical "overeating disease". It is due to Clostridium perfringens type D and most commonly strikes large fast-growing lambs. It is caused by a sudden change in feed that induces the organism, which is already present in the lamb's gut, to proliferate. It is most commonly observed in lambs consuming high concentrate rations. It can also occur when lambs are nursing on heavy milking dams. It usually affects lambs >1 month old. Vaccination of pregnant ewes 30 days before lambing is the best preventative. The best source of control is: 1. hygiene; 2. vaccinate dam at pregnancy; 3. consider vaccinating young lambs when losses are heavy (alternatively, provide immunoglobulin)
Salmonellosis can cause diarrhea in all ages; the circumstances in young lambs are similar to those in calves. It also can cause outbreaks of diarrhea late in pregnancy and in this situation is accompanied by abortion. Salmonellosis is more common when sheep or goats are congregated intensively or stressed, particularly by shipping.
Note: Parasitic diseases tend to occur in lambs older than 1 month, the only exception being cryptosporidiosis as early as 1 week of age. Unlike calves, viruses are not a major recognized cause of diarrhea in lambs. We have seen rotaviral outbreaks in kid goats. Coccidiosis tends to be seen in lambs >1 month, and may occur with nematodiriasis in our area.
Pneumonia often occurs because of a lack of colostrum, because of "mastitis milk," or because ewes are heavily infected with Pasteurella multocida (99% are infected in their upper respiratory tract without disease, so the organism is always present). A lamb contracts pneumonia because it can't stand stresses such as too little milk, draft, dampness, and ammonia off the manure pack. Diagnosis of sick, unthrifty young lambs is relatively simple: most of the time they are either starving or have pneumonia. Strive for early detection and start antibiotic treatment before the lungs are permanently damaged. Treatment for pneumonia is to inject the lamb with antibiotics (tetracycline, penicillin, or streptomycin) plus one grain sulfamethazine per pound of body weight. Adequate selenium and vitamin E help lambs withstand pneumonia.
1. Pregnancy toxemia
Drs. Montgomery and Fox touched on this in their lectures. Pregnancy toxemia is a metabolic disease affecting ewes in late gestation. It most commonly afflicts thin ewes, overfat ewes, and/or older ewes carrying multiple fetuses. It is caused by inadequate intake of energy during late pregnancy, when the majority of fetal growth occurs. The subsequent metabolic changes result in excessive lipid mobilization, especially in the liver. Cold weather, poor feed quality, and environmental stress induce a state of negative energy balance and increase the risk of pregnancy toxemia. Affected ewes are typically lethargic, go off food, and may be dehydrated. There is a simple dipstick test for ketone bodies, which are metabolites that occur in urine. Clinical signs of depression in a fat, late-gestation ewe with twins or triplets should trigger a strong suspicion of pregnancy toxemia. Treatment is to increase the blood sugar supply to the body by administering propylene glycol or molasses orally, or dextrose solution intravenously. In extreme cases, removal of the fetuses by induced abortion is the only recourse to save the ewe. Pregnancy toxemia can be prevented by providing adequate energy to ewes during late gestation, approximately 1 kg of cereal grain/d (2.2 lb cereal grain/d). Adequate feeder space is necessary so that all ewes consume enough feed. Affected ewes must be detected early (within a day) of clinical signs, otherwise they are hard to save. Other treatment options are to do a Caesarian section or to abort the lambs using corticosteroids.
Mastitis is an inflammation of the mammary gland (udder) caused by bacterial infections up the teat canal. Trauma, fecal contamination and teat conformation are factors. Important bacteria causing mastitis in ewes are Staphylococcus aureus and Pasteurella haemolytica. Note that the latter is the cause of pneumonia in lambs, and is a normal inhabitant in the respiratory tract, mouth and pharynx of sheep. There are two types of mastitis: acute and chronic. The glands of ewes with acute mastitis may be discolored, dark, swollen and warm (bluebag). The affected ewe may be reluctant to walk, may hold up one rear foot, and may not permit the lambs to nurse. Ewes with chronic mastitis often go undetected. Severe chronic mastitis with scar tissue formation (hardbag) is a reason for culling. Active mastitis is treated with intramammary infusions of antibiotics and systemic antibiotics. There is no vaccine for mastitis so it is best prevented by good management and sanitation.