Blackleg is characterized by various disease courses, and the duration and frequency of outbreaks vary The disease usually occurs in cattle in the summer and autumn. Poor fodder, including dry grass, increases the risk of the occurrence of an outbreak of blackleg
Cases in animals are registered in dozens of countries around the world (Kazakhstan, USA (California), Austria, Algeria, Pakistan, Taiwan, Zambia, Belarus)
In the Russian Federation, cases of blackleg have been registered each year in various regions (in the Irkutsk Region in 2011, Kursk Region in 2012, Chuvash Republic in 2013, Trans-Baikal Territory in 2014) during grazing seasons, manifesting as sporadic cases or small outbreaks and only rarely as an enzootic disease.
In the acute form, the body temperature of the animal increases to 41–42°C; the animal shows signs of depression, including a refusal to eat and lethargy; and subcutaneous gas oedema forms, especially in the extremities, with swelling and crepitus in the affected muscles In the hyper-acute form, the clinical signs are usually not observed due to the sudden death of the affected animal
The characteristic pathological and anatomical changes are acute necrohemorrhagic emphysematous myositis of the skeletal muscles, most often of the thoracic and pelvic belt muscles expressed pulmonary oedema; myocarditis and petechial hemorrhages on the heart; liver enlargement; and venous hyperaemia of the liver and spleen Visceral myonecrosis is less commonly noted and may affect the heart, hyoid muscles and diaphragm Fibrinous pericarditis occurs very rarely. There are descriptions of damage caused by C. chauvoei in the spleen, liver and kidneys. The spleen severely increased in size, congested and has dark black color. Microscopic studies shower leukocytes infiltrations in sinusoidal spaces and hemorrhages in the liver. Histological sections of kidneys shower hemorrhages, degeneration of renal tubules, necrosis of renal tubules, increased urinary spaces
Blackleg is a preventable, soilborne disease of both cattle and sheep that producers need to be concerned about. It is caused by an anaerobic, soilborne bacterium (Clostridium chauvoei) and is almost always lethal. Animals are usually found deceased and exhibit swelling under the skin which “crackles” when pushing down on it.
Blackleg vaccines, usually 7- and 8-way products, are widely available and are very effective at preventing livestock from contracting this deadly disease.
Animals Affected
Blackleg is a non-contagious but highly fatal disease, with nearly 100% death loss. Animals found alive can be given high doses of penicillin, but outcomes are poor. It is a peracute infection, meaning it is very severe and of very short duration.
It will infect sheep of any age, but it mainly affects cattle from six months to two years of age. However, in rare cases, it may affect calves as young as six weeks and cows as old as 12 years of age. Sadly, this disease usually infects fast-growing, high-performance animals that are growing well.
Cause of Blackleg
Most cases of blackleg are caused by the anaerobic, spore forming bacteria, Clostridium chauvoei. Very few cases are caused by Clostridium septicum. Blackleg gets its name because it typically infects the rear leg muscle, causing it to turn a darkened or black color.
There are more than 60 types of Clostridium bacteria. Clostridial organisms are anaerobes, which means they like to live and grow where there is no oxygen. There are several diseases in cattle caused by different Clostridial species. Some examples are malignant edema (Cl. Septicum), black disease or infectious hepatitis (Cl. novyi), and several types of enterotoxemia (Cl. perfringens types C and D).
Clostridium bacteria have developed the ability to survive extreme environmental conditions by developing into highly resistant spores. As spores, the bacterium can live in soil for many years, waiting for its opportunity to strike and infect a host.
The Di
Maintaining optimum herd health is one of the greatest challenges cattle producers face. Herd losses quickly lead to lost profit; the loss of young heifers, in particular, can mean missed breeding opportunities and fewer head to take to the sale barn. To put this into perspective, in 2015 the total estimated cost of death loss in cattle and calves was $3.87 billion.
Blackleg is a fairly common disease in cattle and can have dire consequences. It can strike without warning, it has a high mortality rate, and its symptoms are not always easy to detect. Fortunately, producers and feedlot operators can take steps to increase the immunity of their herds and reduce the chances that their animals will contract blackleg.
What Is Blackleg?
Blackleg is a clostridial disease that primarily affects young cattle raised on pasture. A clostridial disease is one caused by anaerobic bacteria in the soil. These bacteria have protective coverings known as spores and are often fatal to the animals they infect. More than 60 types of clostridial bacteria exist, though not all of them have the potential to cause disease. Black disease, malignant edema, tetanus and botulism are examples of other serious clostridial diseases.
Blackleg is primarily caused by the clostridial bacterium known as Clostridium chauvoei. Its spores are incredibly widespread — they are found virtually everywhere in the environment. The disease is also known as clostridial myositis.
C. chauvoei was discovered in 1887 and later took its name from a French veterinarian, J.B.A. Chauveau. It is a gram-positive, spore-forming rod that is found in soil and the feces and digestive systems of many animals, such as cattle. The spores are highly resistant to harsh environmental conditions and many disinfecting agents. They can be found in pairs and sometimes in small chains, but most often each single bacterium exists in isolation, though there may be many other bacteria in the surrounding earth.
How Do Cattle Contract Black
Blackleg is an acute, febrile, highly fatal disease of cattle and sheep caused by Clostridium chauvoei and characterized by emphysematous swelling, commonly affecting heavy muscles (clostridial myositis). It is found worldwide.
Etiology:
C chauvoei is found naturally in the intestinal tract of animals. Spores remain viable in the soil for years and are purported to be a source of infection. Outbreaks of blackleg have occurred in cattle on farms in which recent excavations have occurred or after flooding. The organisms probably are ingested, pass through the wall of the GI tract, and after gaining access to the bloodstream, are deposited in muscle and other tissues (spleen, liver, and alimentary tract) and may remain dormant indefinitely.
In cattle, blackleg infection is endogenous. Lesions develop without any history of wounds, although bruising or excessive exercise may precipitate disease in some cases. Commonly, the animals that contract blackleg are of the beef breeds, in excellent health, and gaining weight. Outbreaks occur in which a few new cases are found each day, sometimes for several days. Most cases are seen in cattle from 6–24 mo old, but thrifty calves as young as 6 wk and cattle as old as 10–12 yr may be affected. The disease usually occurs in summer and fall and is uncommon during the winter. Interestingly, in sheep, the disease is almost always the result of a wound infection and often follows some form of injury such as shearing cuts, docking, crutching, or castration. The case fatality rate approaches 100%. In New Zealand, blackleg is seen more frequently in sheep.
Clinical Findings and Lesions:
Blackleg, cow
Blackleg, cow
COURTESY OF THE DEPARTMENT OF PATHOBIOLOGY, UNIVERSITY OF GUELPH.
Usually, onset is sudden, and a few cattle may be found dead without premonitory signs. Acute, severe lameness and marked depression are common. Initially, there is a fever but, by the time clinical signs are obvious, body temperature may be normal or subnorma
Managing disease can be a frustrating proposition. This Guide can help you identify which disease is damaging your cattle.
Blackleg
Blackleg is a highly fatal disease of young cattle caused by the spore forming, rod shaped, gas producing bacteria Clostridium chauvoei.
Clostridia are group of anaerobic, spore-forming organisms found in the soil/environment, which produce rapidly fatal disease by secretion of potent toxins.
Conditions such as botulism, blackleg, bacillary haemoglobinuria, malignant oedema and tetanus are all caused by clostridia.
Most cases occur in young stock between 10 months and two years of age. Feet or legs and the tongue are often the predilection site.
Symptoms
Lameness
Loss of appetite
Rapid breathing
Fever
Unwillingness to move
Treatment
In most cases the animal is found dead without being previously observed sick.
Prevention
Vaccination is available that will protect cattle from a number of different illnesses caused by clostridia.
Blackleg is a highly fatal disease of young cattle caused by the spore forming, rod shaped, gas producing bacteria Clostridium chauvoei. Clostridia are group of anaerobic, spore-forming organisms found in the soil/environment, which produce rapidly fatal disease by secretion of potent toxins.
Blackleg is an acute non-contagious, toxic, infectious disease of livestock and wild animals that is characterized by fever, myositis, systemic infection and rapid mortality. The causative agent of the disease is the obligate anaerobic bacillus Clostridium chauvoei, which persists in soil in the form of resistant spores (1–3). This creates convenient conditions for the formation of endemic zones
Contact of an animal with contaminated soil, water or food leads to the development of the disease (6). According to the common understanding of the pathogenesis of this disease, C. chauvoei spores in contaminated pastures undergo one or more cycles of replication in the intestinal tract without causing the clinical symptoms of the disease (7–9). When an animal experiences an injury that breaks the barrier of the skin and that open wound becomes contaminated with spores, the spores enter an anaerobic environment and germinate. The vegetative form of the pathogen releases toxins that cause the clinical manifestations of the disease, ultimately leading to the death of the host
Blackleg is a fatal disease of young cattle. It produces an acute local infection, and the resulting blood poisoning leads to rapid death. The name 'blackleg' derives from the fact that the site of infection is often a leg muscle, and that the affected muscle is dark in colour
Causes of Blackleg Disease in Cows
A number of different environmental factors increase the likelihood that cattle will contract blackleg disease:
Injury: If a cow sustains an injury, the site of the injury may receive reduced blood flow and, consequently, a reduced amount of oxygen. Reduced oxygen at the injury site may cause the blackleg spores to become active. For this reason, a cow that exhibits noticeable bruising is at increased risk of contracting blackleg disease. Activities such as transport, improper handling, injections, excessive exercise and rough pasture interactions can all cause bruising that may lead to blackleg spore germination and active infection.
Ingestion of contaminated feed: Ingestion of feed that is heavily contaminated with C. chauvoei spores can also lead to infection. After animals consume the contaminated feed, the spores travel to and colonize their muscle tissue. In some cases, after animals ingest large amounts of contaminated feed, bruising or injury is not necessary for the active infection to occur.
Drought: Drought stunts forage growth. As cattle feed on shorter and shorter vegetation, their mouths must come closer to the soil, and their risk of contracting blackleg from soil contact increases. Drought also leads to dry soil that can easily blow away in the wind, spreading spores over the surrounding land.
Recent excavation: Recent excavation projects create a hospitable environment for the spread of blackleg spores. Excavation projects disturb the earth and allow spores to disperse over the ground. Even innocuous-seeming activities such as mucking out stalls or pens can disturb earthen floors and expose cattle to the spores lurking there.
Extreme weather: Many cases of blackleg occur during wet seasons, typically in the summer months. Torrential spring rains and flooding lead to hospitable conditions for the spread of blackleg spores because of the way they disturb the soil. The soil saturation associated with heavy rainstorms
How Do Cattle Contract Blackleg?
Cattle often consume blackleg spores as they graze at pasture. When cattle consume low-growing vegetation, they may ingest some soil — and spores — as well. The spores then travel through the digestive system, pass through the intestinal wall, move through the cow’s bloodstream and disperse throughout the muscle tissue in the animal’s body, where they may remain dormant for some time. The spores often end up in the musculature of an animal’s legs, especially the hind legs, though they can also infect areas such as the tongue, diaphragm, udder or brisket. Experts are unsure why the spores so often colonize muscle tissue in preference to other types.
Lack of oxygen to the muscle tissues can cause the spores to emerge from their dormancy. When the spores become active, they proliferate rapidly and cause gas gangrene in the muscles, which quickly leads to the characteristic dark-colored lesions that give the disease its name. Tissue necrosis and toxemia generally result, as well. Though blackleg does not always cause outward discoloration, cutting into a diseased animal’s infected leg will reveal areas of darkened tissue where gas gangrene has formed. If superficial muscles are involved, a darkening of the observable tissue of the affected legs is also common.
Active blackleg infections ultimately prove fatal in a majority of cases. Many necropsies reveal inflammation in the hearts of cattle that have died from blackleg, particularly fibrinous pericarditis and necrotizing myocarditis, in addition to lesions and necrosis in their skeletal muscles.
It’s important to note that although blackleg is infectious, it is not contagious from individual to individual. So an infected animal cannot spread the disease directly to other members of the herd. It is also not necessary for cattle to have open wounds to contract blackleg — consumption and subsequent bruising and injury are sufficient to activate the disease.
Blackleg in Calv
Blackleg is a clostridial disease that primarily affects young cattle raised on pasture. A clostridial disease is one caused by anaerobic bacteria in the soil. These bacteria have protective coverings known as spores and are often fatal to the animals they infect. More than 60 types of clostridial bacteria exist, though not all of them have the potential to cause disease. Black disease, malignant edema, tetanus and botulism are examples of other serious clostridial diseases.
Blackleg is primarily caused by the clostridial bacterium known as Clostridium chauvoei. Its spores are incredibly widespread — they are found virtually everywhere in the environment. The disease is also known as clostridial myositis.
C. chauvoei was discovered in 1887 and later took its name from a French veterinarian, J.B.A. Chauveau. It is a gram-positive, spore-forming rod that is found in soil and the feces and digestive systems of many animals, such as cattle. The spores are highly resistant to harsh environmental conditions and many disinfecting agents. They can be found in pairs and sometimes in small chains, but most often each single bacterium exists in isolation, though there may be many other bacteria in the surrounding earth.
Blackleg is an infectious, non-contagious disease caused by Clostridium chauvoei. Infection occurs when animals ingest bacterial spores while grazing. The bacterial spores penetrate the intestine and are disseminated via the bloodstream to the skeletal muscle, where the spores remain dormant. Following an event that causes low oxygen conditions (i.e. bruising or damage to the muscle) in infected tissue, the spores germinate, multiply and produce toxin that results in muscle necrosis and hemorrhage. The animals affected by blackleg are usually well fed animals between 6 months and 2 years of age. The cause of death in affected cattle is usually acute toxemia. The course of the disease is often between 12-48 hours and clinical signs are often absent; however, animals may exhibit signs of lameness, tachycardia, fever, anorexia, rumen stasis and lethargy. Blackleg is primarily a disease of pastured cattle with the majority of the cases occurring during the summer months.
Throughout 2017, the Texas A&M Veterinary Medical Diagnostic Laboratory (TVMDL) diagnosed a significantly increased number of blackleg cases. Although a cause for the increased incidence of cases has not been conclusively determined, a possible explanation are the environmental changes that resulted from the unusual weather conditions experienced during 2017. Specifically, it is speculated that the extreme amounts of rain and flooding associated with Hurricane Harvey and the subsequent dry conditions worked to stir up the soil leading to exposure of deeply hidden bacterial spores.
Epidemiology
Blackleg affects mainly non vaccinated cattle between 6 mo and 2 y of age, with occasional cases occurring in animals outside this age range. The disease affects mostly animals in good nutritional condition, often on pasture
Despite the frequently repeated claim that both spores and vegetative forms of C. chauvoei are found in feces of healthy and sick animals, little information is available in this regard in the scientific literature. The current, but unproven, dogma is that regardless of the origin, the spores of C. chauvoei can contaminate the soil, survive in the environment for decades, and can infect animals grazing on contaminated pastures Falquet et al., Infections by C. chauvoei of mostly unknown pathogenesis have been reported in goats, deer, oryx, elephants, horses, pigs, mink, fresh-water fish, whales, frogs, and hens. Gas gangrene and enterocolitis [8] associated with C. chauvoei have been reported, very rarely in humans
Transmission: Mode of transmission: In sheep the disease is almost always wound infection. Infection of such wounds at hearing and docking and of the novel of birth may cause the development of local lesson. Infections of the vulvas and vagina of the ewe and rams up to year old, usually as a result of infection of skin would case by fighting. Occasional out breaks have occurred in sheep after vaccination against enterotoxaemia. Ewes exposed to infection at shearing develop typical lesion but ewes traded with penicilling are un affected except that the present ewe in the letter group shown distended abdomens, weakness and recumbence due to edema and gas formation in cattle mainly transmited through injection of spores
Risk factor: Animal risk factor: True blackleg is usually thought as disease of cattle and occasionally sheep but out breaks of the disease has been recorded in deer and in one case in a horse. In cattle the disease is largely confined to young stock between the age of 6 month and 2 years. In the field the di
Blackleg is an infectious bacterial disease of cattle and rarely of other ruminants. This bacteria is caused by Clostridium chauvoei which is an anaerobic, gram positive, motile, rod-shaped bacillus bacterium and persists in the soil as resistant spores. Blackleg is an acute or subacute but chronic disease may occur. It occurs most frequently in animals 6-24 months of age and the disease mainly affects none vaccinated as well as animals in good nutritional condition. It produces persistent spores when conditions are not ideal and spores are highly resistant to environmental factors and disinfectants. Infected ruminants do not directly transmit the disease to other animals. The bacteria enter the body through the alimentary mucosa after ingestion of contaminated feed. Secretion of cytolytic toxins that cause necrosis of vascular endothelia .The toxins are absorbed into the animal’s bloodstream which makes the animal acutely sick and causes rapid death. Economic importance due to blackleg is loss of animals, milk production and draft oxen, and cost for treatment and vaccination. Fatality rate of blackleg in fully susceptible populations approaches 100%. Clinical Signs include lethargy anorexia, reluctance to move lameness and recumbence. When superficial muscles are affected, swelling and crepitus are evident. Cattle found dead of blackleg are lying on the side with the affected hind limb stands out stiffly, bloating and putrefaction occur quickly and bloodstained from exudates, nostrils and anus. The disease can be diagnosed using laboratory diagnosis, Immune Fluorescent, Cell Culture and PCR. Control and prevention relies mainly on vaccination.
Blackleg is an endogenous acute infection that principally affects cattle, whose etiologic agent is the anaerobic bacterium Clostridium chauvoei. In recent years, the major virulence factors of C. chauvoei have been discovered and described. However, the pathogenesis of blackleg in cattle, and in particular, the movement of the pathogen from the point of entry to the affected tissues is not yet fully elucidated. Disease control is based on appropriate management and vaccination. This review summarizes the latest research findings that contribute toward the understanding of the disease in cattle, provide a foundation to preventive strategies, and identify future research needs.
