Animal Diseases – Small Ruminants
Ovine / Sheep, Caprine / Goat

Bluetongue virus (BTV)

Epidemiology
Bluetongue, or catarrhal fever, is caused by a double-stranded RNA virus of the genus Orbivirus and family Reoviridae. It is a noncontagious disease transmitted by insects to wild and domesticated ruminants, especially sheep.

Signs
Seven or eight days after infection, sheep develop acute signs—high temperature, lethargy, and self-isolation from the herd. Shortly after the rise in temperature, the buccal mucosa becomes red and swollen, and large volumes of foamy saliva are produced. The tongue swells up and in some cases turns blue (hence the name of the disease). The crown of the unguis becomes red and painful. Affected animals can limp and ewes may abort. In most cases, growth is retarded and there is coat loss. Severely affected sheep may die eight to 10 days into the infection.

In cattle and goats, the infection is usually asymptomatic. When there are signs in cattle, the most common are hyperthermia, abortion towards the end of gestation (in the eighth month), edema (of the udders, teats, vulva, and hocks), and erythema (mucosa, teats, and udders).

The spread of BTV
Bluetongue was first reported in 1876 in South Africa. While it used to be believed that is was confined to Africa, over the last 10 years the disease has spread to Asia, the southern United States, Australia, and southern Europe. A total of 24 different serotypes of the bluetongue virus are known, of which eight have been reported in Europe (serotypes 1, 2, 4, 6, 8, 9, 11, and 16).

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Border disease (BD)Top

Epidemiology
The BVD virus is a small, single-stranded RNA virus belonging to the genus Pestivirus. Two other animal viruses belong to this genus, namely the viruses that cause border disease (BD) in sheep and classical swine fever (CSF) in pigs.The virus that causes bovine viral diarrhea (BVD) was first identified in 1946. The disease is found throughout the world and its prevalence among animals exposed to the virus ranges from 30–80% in different countries and regions.

BVD impacts fertility in the herd
The infection compromises the herd's fertility and induces the return of heat following death of the embryo when the cow is infected between the first and second months of gestation. Abortion and birth defects are possible throughout gestation.

BVD-PI animals serve as a reservoir of infection
A common consequence of prenatal infection by members of this viral genus is the birth of infected offspring that are permanently immunotolerant (BVD-persistent infection (BVD-PI)), which disseminate the virus throughout the herd. BVD-PI animals (i.e., those infected between the second and the fourth months of gestation) carry the virus throughout their lifetime and constantly secrete large numbers of viral particles. This group therefore constitutes a major source of infection for the rest of the herd. In addition, BVD-PI animals sooner or later develop the fatal form of BVD called mucosal disease (MD). The number of BVD-PI animals in an infected herd is of the order of 1% (although the percentage can be as high as 27%) and detecting them is primordial in the control of Pestivirus disease.

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Bovine viral diarrhea (BVD)Top

Epidemiology
The BVD virus is a small, single-stranded RNA virus belonging to the genus Pestivirus. Two other animal viruses belong to this genus, namely the viruses that cause border disease (BD) in sheep and classical swine fever (CSF) in pigs.The virus that causes bovine viral diarrhea (BVD) was first identified in 1946. The disease is found throughout the world and its prevalence among animals exposed to the virus ranges from 30–80% in different countries and regions.

BVD impacts fertility in the herd
The infection compromises the herd's fertility and induces the return of heat following death of the embryo when the cow is infected between the first and second months of gestation. Abortion and birth defects are possible throughout gestation.

BVD-PI animals serve as a reservoir of infection
A common consequence of prenatal infection by members of this viral genus is the birth of infected offspring that are permanently immunotolerant (BVD-persistent infection (BVD-PI)), which disseminate the virus throughout the herd. BVD-PI animals (i.e., those infected between the second and the fourth months of gestation) carry the virus throughout their lifetime and constantly secrete large numbers of viral particles. This group therefore constitutes a major source of infection for the rest of the herd. In addition, BVD-PI animals sooner or later develop the fatal form of BVD called mucosal disease (MD). The number of BVD-PI animals in an infected herd is of the order of 1% (although the percentage can be as high as 27%) and detecting them is primordial in the control of Pestivirus disease.

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BrucellosisTop

Overview
Brucellosis is an infectious disease caused by Brucella bacteria. Brucella species of major concern are B. abortus, primarily affecting cattle; B. melitensis, primarily affecting sheep and goats; and B. suis, primarily affecting pigs. All these Brucella species are non–host-specific and may be transmitted to other animal species or humans under appropriate conditions.

Brucellosis is commonly transmitted to susceptible animals by direct contact with infected animals or in an environment that has been contaminated with discharges from infected animals. Brucellosis is thus a herd or flock problem.

Brucellosis is a notifiable disease, and any occurrence of it has to be reported to the local health authority. Depending on the species and the infection rate, different eradication programs are effective. Where incidence rates are high, vaccination programs are necessary to lower the infection rate. Once this has been achieved, surveillance programs linked to slaughter of infected animals are introduced. These programs lead to “Brucellosis-Free” and “Officially Brucellosis-Free” status for specified regions or whole countries. In Europe, surveillance is regulated in the EU directive 2003/99/EC on Monitoring of Zoonoses.

Signs
Common symptoms of Brucella infection are decreased milk production, weight loss, abortions, infertility, and lameness. Brucella uptake occurs orally, or via skin wounds or mucous membranes. Brucella bacteria are mainly excreted with aborted placentas and fetuses, and with semen and milk.

Occasionally, animals may recover after a period of time. More commonly, however, the symptoms disappear but the disease prevails. Such asymptomatic animals are dangerous sources of infection.

Human health risk
Raw milk and unpasteurized cheeses represent the most frequent sources of human infection. Farmers and veterinary staff run an increased risk of infection due to direct exposure to aborted infected materials. In humans the disease is usually not fatal, but if untreated it can last for many years.

The incubation period is usually 1 to 3 weeks but can sometimes be as long as several months. Patients show nonspecific symptoms such as undulating fever, chills, malaise, and headache.

Economic impact
Brucellosis is a major public and animal health problem in many regions of the world. Although it rarely kills infected animals, considering the economic damage the disease can cause, brucellosis is one of the most serious livestock diseases worldwide.

This zoonosis has been or is close to being eradicated from a number of countries, but it is still prevalent in the Mediterranean region, Africa, Asia, and South America.

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Caprine arthritis encephalitis (CAE) Top

Epidemiology
CAE and maedi-visna are persistent viral infections caused by closely related lentiviruses belonging to the Retroviridae family. Although there are only a few documented cases of interspecific transmission, CAEV can infect sheep and maedi-visna can infect goats.

The infection is transmitted very early to the lamb or kid via the dam in colostrum or milk, or via the respiratory secretions of infected animals. Now a permanent carrier, the lamb or kid can transmit the virus to the rest of the flock throughout its life.

Signs
CAE is a disease that affects caprines, causing arthritis and mastitis in adults and encephalitis in younger animals. Maedi-visna is a disease of sheep, causing shortness of breath or respiratory distress, arthritis, and weight loss. In addition, some ovines develop lesions of variable severity in the lungs and on the udders. CAEV and maedi-visna are closely related viruses.

Prevalence
Although ovine lentiviruses have been identified in most countries where sheep are raised (apart from Australia and New Zealand), CAEV is more widespread in industrialized countries.

Disease-free status requires serological testing
Serological screening for both viruses is required for the certification of caprine and ovine breeding units. Symptoms only manifest in a fraction of seropositive animals (9%–38%, depending on the study).

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ChlamydiosisTop

In ruminants, chlamydiosis is a contagious disease caused by a bacterium that also infects birds and humans. It can cause abortion, premature delivery, pneumonia, conjunctivitis, and arthritis in ruminants. The infection can be transmitted to the newborn, young, or adult ruminant by the large numbers of bacteria excreted in fetal envelopes and fluids, feces, urine, and milk, although the main route of infection is via the inhalation of contaminated aerosols. Chlamydia taxonomy was revised by Everett in 1999. In the new classification, the species are divided between two main genera:

  • The genus Chlamydia, which includes C. trachomatis (humans), C. suis (pigs), and C. muridarum (mice and hamsters)
  • The genus Chlamydophila, which consists of six species, namely Cp. abortus (mammals), Cp. psittaci (birds), Cp. felis (cats), Cp. caviae (guinea pigs), Cp. pecorum (mammals), and Cp. pneumoniae (humans)

In ruminants, two species have been identified: Cp. abortus (which causes abortion) and Cp. pecorum (which causes asymptomatic gut infection, pneumonia, conjunctivitis, arthritis, abortion, and infertility). In pregnant women, C. abortus can also induce abortion with serious complications.

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Clostridium perfringensTop

Overview
A spore-forming, anaerobic bacterium, Clostridium perfringens is commonly found in the soil and digestive tracts of various domestic animals and is categorized into six unique types (A, B, C, D, E, and F), with Type-B, -C, and -D being the most common forms of the disease.

It is not uncommon for small amounts of C. perfringens to inhabit and pass through the digestive tract of an animal without causing disease. But in instances where an animal is exposed to a sudden increase in carbohydrates (milk, supplementary concentrates, etc.) C. perfringens can rapidly increase in numbers, producing large amounts of toxin that often cause rapid death.

Type-B, also known as lamb dysentery, presents a high mortality rate in young lambs and is also linked to disease in young calves.

Type-C typically affects cattle, small ruminants, and swine, where it can contribute to hemorrhagic and necrotic enteritis.

Type-D, also known as “pulpy kidney disease” or "overeating disease,” is associated with small ruminants and cattle. C. perfringens Type-A and -C can also cause enterocolitis (swelling of the small and large intestines) in foals, where stock-horse breeds such as quarter horses are more susceptible.

Signs
Because of the aggressive nature of the disease and rapid onset of death, it can be challenging to observe clinical signs in an infected animal. Upon closer examination of an animal prior to death, C. perfringens may present a variety of signs such as excitement, circling, headpressing, convulsions, listlessness, diarrhea, colic, or a disinterest in nursing.

Human health risk
It does not appear that C. perfringens presents a zoonotic risk.

CryptosporidiosisTop

Overview
Cryptosporidiosis is caused by microscopic intestinal parasites that are excreted in the feces of an infected animal. Found throughout the world, the parasites commonly interact with other enteropathogens to produce diarrhea and intestinal injury in neonatal farm animals such as piglets, kids, lambs, and foals.

Studies have shown that concurrent infections with other pathogens such as coronavirus and rotavirus can result in more severe diarrhea. While mortality rates in cryptosporidiosis are usually low, fatalities can occur when complicated by other factors such as an animal experiencing energy deficit as a result of low colostrum/milk intake, concurrent infections, or chilling caused by adverse weather conditions.

Transmission of the disease may occur directly from animal to animal, or indirectly from environmental contamination, fecal contamination (water or feed supply), or human transmission. Infection in calves can be detected at as early as 5 days of age, with diarrhea occurring between 5–15 days of age.

In small ruminants, infection can be associated with severe outbreaks of diarrhea, resulting in high mortality rates in lambs 4–10 days of age, and goat kids 5–21 days of age.

Although cryptosporidiosis is not generally regarded as an important enteric pathogen in swine, infections can be seen over a broader age range (1 week of age up to market age), and can contribute to post-weaning malabsorptive diarrhea in infected swine.

Cryptosporidiosis is less prevalent in foals, but when infection does occur it is typically at 5–8 weeks of age.

Signs
Signs of cryptosporidiosis can include diarrhea that persists for several days, significant weight loss, emaciation, apathy, anorexia, and dehydration.

Human health risk
Cryptosporidium can be a common nonviral cause of diarrhea in immunocompetent persons (e.g., children) and can have a severe health impact on immunocompromised persons. Infected animals can transmit the disease directly to humans, and there is also a risk of the cryptosporidiosis being transmitted through surface and drinking water that has been contaminated with the feces of an infected animal.

Fasciola hepaticaTop

Overview
Fasciola hepatica is seen in a broad range of hosts worldwide, including cattle and sheep, where the infection will present itself in one of three forms: chronic, which contributes to a high mortality rate in sheep but few fatalities in cattle; acute, which is often fatal in sheep; and in combination with a secondary infection such as infectious necrotic hepatitis that yields frequent fatalities in sheep.

The disease is transmitted through the ingestion of aquatic vegetation containing encysted cercariae that have emerged from infected lymnaeid snails. After ingestion, young flukes are released into the animal’s duodenum, travel to the liver, and eventually reside in the parenchyma for several weeks, where they grow and destroy tissue.

While most flukes are shed by cattle in <6 months, adult flukes can live within the bile ducts of sheep for several years.

Signs
In cases of acute fasciolosis, signs can include distended abdomen, anemia, and sudden death, usually within 6 weeks of infection. Subacute signs of the disease are typically anemia and hemorrhage, and result in death 7–10 weeks after infection.

Chronic fasciolosis signs may involve anemia, edema, and reduced milk secretion.

Human health risk
Fasciolosis can be transmitted to humans through the ingestion of contaminated drinking water and freshwater plants in endemic areas, or the consumption of poorly cooked sheep liver. After infected material has been ingested, cercariae encyst in the duodenum, develop into larvae, and eventually penetrate through liver tissue into the biliary tract.

Economic impact
Liver fluke can cause significant economic consequences by greatly impairing feed efficiency, growth, and fertility in both cattle and sheep.

Foot and mouth disease (FMD)Top

Overview
Foot and mouth disease (FMD) is a highly contagious disease that affects all cloven-hoofed animals, and is widespread throughout the world. FMD cannot be differentiated clinically from other vesicular diseases such as swine vesicular disease (SVD).

The virus is a member of the genus Apthovirus and the family Picornaviridae. There are seven serotypes of FMD virus: O, A, C, SAT 1, SAT 2, SAT 3, and Asia 1. Infection with any one serotype does not confer immunity against one of the other serotypes.

Of the domesticated species, cattle, pigs, sheep, and goats are susceptible to FMD.

Signs
Clinical signs of FMD are the appearance of vesicles (small blisters) on the feet, in and around the oral cavity, and on the mammary glands of females. Vesicles can also occur inside the nostrils and at pressure points on the limbs, especially in pigs.

Transmission generally occurs through contact between infected and susceptible animals. The virus can be excreted into the air during the acute phase of infection.

Human health risk
It does not appear that FMD presents a zoonotic risk.

Economic impact
The presence of FMD is a very important economic threat to the livestock industry, due to the culling of herds and the restriction on meat exports from affected areas.

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Maedi-visnaTop

Overview
Maedi-visna (MV), ovine progressive pneumonia (OPP), and caprine arthritis-encephalitis (CAE) are chronic diseases of sheep and goats that are typically grouped together as small ruminant lentiviruses (SRLVs). Maedi-visna is an Icelandic name that describes two of the syndromes associated with the MV virus. “Maedi” translates to “labored breathing” and refers to the interstitial pneumonitis aspect of the disease; and “visna” translates to “wasting”, which is a sign associated with paralyzing meningoencephalitis.

Ovine lentiviruses have been identified in sheep-rearing countries throughout the world, with the exception of New Zealand and Australia, and CAEV is primarily found within industrialized countries, coinciding with the international transport of dairy goats (European breeds).

The virus affects all breeds of sheep and goats, but studies have shown that some breeds may have a greater resistance to the lentivirus infection. Transmission of MV and CAEV primarily occurs via the oral route by ingestion of infected colostrum or milk, or by inhalation of infected aerosol droplets.

Signs
The predominant signs in clinically affected sheep are emaciation and respiratory distress, whereas polyarthritis is the primary sign displayed in goats. Fever, coughing, and bronchial exudates are potential but seldom seen signs, unless secondary bacterial infection occurs. Circling, muscle tremors, and paralysis are typically associated with the encephalitic form of the virus.

Human health risk
It does not appear that MV presents a zoonotic risk.

Economic impact
Control programs have helped to decrease MV incidence in some countries, but the disease is still widespread in various parts of the world. For example, within the US infection rates of sheep can exceed 50% in some areas, with midwestern and western states reporting some of the highest rates. Infections are typically asymptomatic, but once clinical signs emerge MV is typically progressive and fatal.

Q feverTop

Epidemiology
Q (Query) fever is an ubiquitous zoonosis that is found throughout the world (apart from New Zealand). It is caused by Coxiella burnetii, an obligate intracellular bacterium that can infect many different animal species, including ruminants, dogs, cats, birds, and arthropods as well as humans. In ruminants (which are believed to be the main reservoir for human infection), the disease is mainly associated with reproductive dysfunction. It usually remains asymptomatic and is not usually screened for unless an animal has aborted several times or shows reproductive problems. Coxiella burnetii colonizes the placenta and causes premature delivery, low birth weight, and abortion.

Impact of Q fever on humans
The main route of infection in humans is through the inhalation of contaminated aerosols, but pregnant women should not drink unpasteurized milk or consume dairy products made with untreated milk. Q fever often goes unnoticed because it can be mistaken for an influenza-like syndrome. The consequences can be dramatic in pregnant women (abortion or premature delivery) and in immunodeficient subjects or patients with valvular heart disease.

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NeosporosisTop

Epidemiology
Neospora caninum is a protozoan parasite first observed in dogs, in which it causes myositis and encephalitis. However, in the 1990s it was observed that Neospora was a major cause of abortion in cows, usually between the fourth and seventh months of gestation. Depending on the number of infected cows in the herd, the abortion rate ranges from 5–30%; the higher rates are characterized by serial abortions occurring in less than a month.

Transmission
It is not fully understood how the parasite is transmitted, but the main route seems to be from mother to offspring, with at least 80% of the calves born to seropositive cows infected. In addition, it has been suggested that dogs may be involved in the transmission of Neospora to bovines. This infection is known on all continents and is the leading cause of bovine abortion in some countries (ahead of BVD and IBR).

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Paratuberculosis (MAP/Johne’s disease)Top

Overview
Paratuberculosis, also known as Johne ’s disease, is caused by the presence of the Myobacterium avium subspecies paratuberculosis in the small intestine of ruminants. It is a worldwide animal health problem, especially affecting beef and dairy herds.

Paratuberculosis is a chronic debilitating enteritis, and its presence in an animal herd can have serious effects on production.

Diagnosis of clinical infection is usually confirmed by the demonstration of the causal organism, M. avium subsp. paratuberculosis, in feces or intestinal tissues post-mortem. The identification of subclinical disease in animals, which can shed the organism over long periods and thus be the source of infection for other members of a herd, is more difficult. The prevalence of bovine paratuberculosis in Europe varies from country to country, ranging from 7% to 55%.

Signs
The signs—chronic inflammation of the intestine, mesenteric lymph node lesions, diarrhea, weight loss, and edema—usually appear in animals of over 2 years of age with an advanced stage of the disease.

Human health risk
The causative bacterium of paratuberculosis, M. avium subsp. paratuberculosis, is known to survive pasteurization of milk and other dairy products, and therefore could be a risk to human health. Increasing scientific evidence indicates that there is a link between paratuberculosis in dairy herds and Crohn’s disease in humans. Crohn’s disease is an incurable, chronic inflammatory bowel disease.

Economic impact
Paratuberculosis in domestic livestock may entail significant economic losses due to several factors, such as reduced production, premature culling, and veterinary costs. In the United States, paratuberculosis is of growing concern to the cattle industry because the presence of the disease impacts international marketing of cattle and cattle products, causing economic losses to producers. Consequently, a voluntary Johne's Disease Herd Status Program for Cattle (VJDHSP) has been established. In April of 2002, USDA-APHIS-Veterinary Service incorporated parts of this program into its national program standards.

Within the European Union, there are no official programs in place; however, country-specific policies apply.

Australia has a National Johne’s Disease Control Program (NJDCP) that aims to reduce the spread and impact of Johne’s disease. It is a cooperative program involving the Australian livestock industries, government, and veterinary profession. Animal Health Australia manages the program on behalf of these key stakeholders.

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Neonatal gastroenteritisTop

Epidemiology
Diarrhea is a major cause of death in calves and other young ruminants. This form of neonatal gastroenteritis is caused by ingested microorganisms that reach the gut. Many different microorganisms can cause neonatal diarrhea, including viruses (rotavirus, coronavirus), bacteria (Salmonella, enterotoxinogenic Escherichia coli K99), and protozoa (Cryptosporidium parvum, coccidia).

Signs
Viral infection often paves the way for bacterial superinfection, which exacerbates the problem and prejudices the outcome. The first signs of diarrhea are loss of appetite, abdominal retraction and tightness, and lethargy. In animals, diarrhea can quickly lead to dehydration followed by paralysis, circulatory failure, and death.

Laboratory testing needed for diagnosis
The causative agent of calf diarrhea cannot be identified on the basis of the symptoms alone; laboratory testing is required. The best prophylaxis against neonatal diarrhea is to ensure that the calf is given an adequate dose of colostrum as soon as possible after delivery.

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Ovine herpesvirus type 2 (gangrenous coryza)Top

Epidemiology
Gangrenous coryza is a disease of large ruminants and pigs, characterized by high fever and usually fatal. Gangrenous coryza is caused by a virus belonging to the genus Rhadinovirus (of the Herpesviridae family), specifically, one of two different gamma-herpesviruses. The natural host of Alcelaphine herpesvirus 1 (AIHV-1) is the wildebeest, in which the infection is silent. The disease appears in various parts of Africa and in a wide variety of ruminant species in zoological parks. Ovine herpesvirus 2 (OvHV-2) is prevalent in all races of domesticated sheep, in which it causes a subclinical infection.

Signs
Found in most parts of the world, the disease's clinical manifestations can vary enormously, from an acute form with mild symptoms to a more typical form with high fever, erosive ulceration of the gastrointestinal mucosa, keratoconjunctivitis with corneal opacity, and copious ocular and nasal discharge.

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Rift Valley fever (RVF)Top

Overview
Rift Valley fever (RVF) is categorized as a bunyavirus and is an acute zoonotic disease that affects ruminants throughout the Arabian Peninsula, Africa, and Madagascar. During periods of epidemic, high abortion and mortality rates can occur among young animals, and humans will often experience an influenza-like disease.

RVF may be transmitted by the movement of animals infected with the virus or by various species of wind-borne mosquitoes. Instances of RVF generally reach their peak during summer, and at the sign of first frost, insect vectors and the disease will typically disappear. In warmer regions, the disease and vectors may be present year-round.

Signs
Common signs of RVF may include lethargy, fever, unwillingness to feed, abdominal pains, jaundice, and diarrhea. In some cases, abortion may be the only sign of infection that an animal displays.

Human health risk
It is possible for humans to be infected with RVF via contact with infected animal tissue or aborted fetuses, mosquito bites, or blood aerosols generated during the slaughter of an infected animal.

RotavirusTop

Overview
Bovine rotavirus is categorized within the Reoviridae viral family, and along with coronavirus, contributes to >50% of the diarrhea problems in calves. While rotavirus is common in cattle herds, other animals such as pigs, chickens, sheep, horses, and rabbits are also susceptible to the disease.

The virus enters through the small intestine, attacking villi and making it difficult for material to be effectively absorbed into the animal’s body. This condition leads to water loss from the epithelial cells and body, causing dehydration and potentially death if there is significant dehydration and emaciation.

Transmission generally occurs when an unaffected animal has oral contact with infected feces and contaminated feed, or if they are exposed to living quarters with poor hygiene characteristics. Cows displaying signs and symptoms may shed the virus for as long as a week, while some cows can become reinfected and shed the virus throughout their life and remain asymptomatic.

Signs
The primary sign of rotavirus is a runny, often yellow diarrhea that contains mucous, blood, or both. Additionally, the animal may become lethargic and have a disinterest in drinking or feeding, which could result in mild to severe dehydration, depending on the animal and the circumstances.

Human health risk
Bovine and human rotavirus strains are specific to their hosts and are not considered a transmission risk from one species to another.

Economic impact
Significant economic loss may occur due to increased morbidity and mortality in neonatal ruminants, treatment costs, and reduced growth rates.

Schmallenberg virusTop

Epidemiology
The Schmallenberg virus belongs to the Bunyaviridae family, genus Orthobunyaviridae and is closely related to Akabane, Aino, and Shamonda viruses. This virus was first identified in November 2011 in Germany. It was found in several samples coming from bovine and ovine hosts showing atypical symptoms, not characteristic of known diseases at the time.

Signs
This virus induces weak clinical symptoms affecting the global health of the animal, such as hyperthermia, loss of appetite, decreased milk production, and in some cases, diarrhea. Infection of female ruminants during gestation can also result in the birth of malformed animals (e.g., hydrocephalus).

Diagnostics
Virus detection is optimally performed using the brain of an aborted fetus, but the virus can also be detected in blood, serum, and the spleen (FLI—German National Reference Laboratory).

ToxoplasmosisTop

Overview
Toxoplasmosis is caused by the protozoan parasite Toxoplasma gondii, which belongs to the family Sarcocystiidae. Toxoplasma infections are widespread in humans and many other species of warm-blooded animals, including pigs, sheep, and goats. Occurrence is worldwide; however, the prevalence in human and animal populations varies greatly among countries.

Infections occur as a result of consuming raw or undercooked meat that contains tissue cysts, and tachyzoites, or by food or water contaminated with oocysts. Toxoplasma-infected meat and meat products are considered to be an important source for human infection.

Signs
The clinical signs include fever, diarrhea, cough, dyspnea, icterus, seizures, and death. T gondii is also an important cause of abortion and stillbirth in sheep and goats, and sometimes in pigs. After infection of a pregnant ewe, tachyzoites spread via the bloodstream to placental cotyledons, causing necrosis. Tachyzoites may also spread to the fetus, causing necrosis in multiple organs.

Human health risk
In humans, toxoplasma infections are also mostly asymptomatic. Clinical signs are mostly known to appear in immunosuppressed individuals, where an infection can cause severe neurological disease. Recent studies have shown, however, that immunocompetent people may develop clinical toxoplasmosis more frequently than previously thought. The Panel of Biological Hazards considers toxoplasmosis to be an under-detected and under-reported disease in the European Union (The EFSA Journal 2007; 583: 1-64), and has recently ranked “Toxoplasma gondii and pathogenic verocytotoxin-producing Escherichia coli (VTEC) as the most relevant biological hazards for meat inspection of sheep and goats” (The EFSA Journal 2013; 11(6): 3265).

The Emerging Pathogens Institute of the University of Florida ranks toxoplasmosis as the number 2 public health burden among food-borne infections, in its publication “Ranking the Risks: The 10 Pathogen-Food Combinations with the Greatest Burden on Public Health.”

Economic impact
Because of the risk of human infection, the meat production industry can be severely affected when a toxoplasma infection occurs. Surveillance and diagnosis of infected pig, sheep, and goat herds can be easily achieved by testing for Toxoplasma antibodies in the animals’ serum, plasma, or meat juice.

Toxoplasma in small ruminants causes losses to herds due to abortions, stillbirths, or the birth of weak lambs. The implementation of appropriate measures—based on the test results—can significantly improve the health status of a herd.

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Transmissible spongiform encephalopathyTop

Overview
Transmissible spongiform encephalopathies (TSEs) are infectious diseases of the brain that affect animal species in various forms, such as bovine spongiform encephalopathy (cattle), scrapie (goat and sheep), and chronic wasting disease (deer). The diseases are caused by altered prion proteins that are resistant to chemicals and heat and that do not easily decompose biologically, often surviving in soil for several years.

The diseases are reported worldwide, with bovine spongiform encephalopathy (BSE) found most frequently in Europe, and chronic wasting disease (CWD) being most prevalent in North America. TSEs cause a slow degeneration of the central nervous system that ultimately leads to the death of an animal, and there is often a significant lapse of time between an animal becoming infected with the disease and displaying the first symptoms. As an example, at the point of infection, cattle may not show clinical symptoms for up to 6 years, and sheep may not show signs for up to 4 years.

Transmission of BSE in cattle occurs through ingestion of feed containing contaminated bone and meat meal. Transmission does not appear to occur naturally between cattle, though some evidence suggests there may be a maternally associated risk for calves born to infected cows. While pathogenesis details are unknown, studies have shown that after the agent enters the animal through oral exposure, it replicates in the Peyer’s patches of the ileum and migrates to the central nervous system via peripheral nerves.

Signs
Clinical signs of TSEs are often subtle and may include nervousness, aggression, low head carriage, ataxia, tremors, and increased sensitivity to touch (hyperesthesia). Animals may also have a reluctance to be milked and experience weight loss and diminished milk production.

Human health risk
Humans can develop a form of TSE known as Creutzfeldt-Jakob Disease (vCJD) by consuming food products that have been contaminated with bovine spongiform encephalopathy. Initiatives are in place to remove high-risk bovine tissue from the human food chain, and for products containing bovine proteins (cosmetics, pharmaceuticals, etc.), measures have been instituted to help ensure that raw materials are sourced from BSE-free geographies.

Economic impact
TSEs can contribute to significant economic losses, whether it be culling of animals linked to BSE or scrapie cases, the destruction of specified risk material (SRM) derived from ruminants (cattle, sheep, and goat), or the impact that export restrictions in affected areas may have on the meat industry as a whole.

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