Bluetongue Disease

Bluetongue disease is a non-contagious, viral disease that primarily affects ruminants such as sheep, cattle, goats, and deer. It is caused by the Bluetongue virus (BTV), which belongs to the Orbivirus genus within the Reoviridae family. The virus is transmitted by biting midges of the Culicoides species, which act as biological vectors. The disease is named after one of its hallmark symptoms: swelling and cyanosis (blue discoloration) of the tongue in severely affected animals.

The clinical manifestations of Bluetongue vary among species. In sheep, particularly European breeds, the disease can be severe, leading to high fever, excessive salivation, facial and tongue swelling, nasal discharge, lameness, and weight loss. In some cases, mortality rates can reach up to 70%. Cattle and goats often experience milder or asymptomatic infections but can serve as reservoirs for the virus, allowing it to spread through midge vectors to more susceptible species. Deer and other wild ruminants can also be affected, sometimes experiencing high mortality rates.

Bluetongue has significant economic consequences due to trade restrictions, loss of livestock productivity, and costs associated with surveillance, vaccination, and vector control. The disease has historically been confined to tropical and subtropical regions, but climate change has expanded its range. Rising global temperatures and changes in precipitation patterns have facilitated the northward migration of Culicoides midges, leading to outbreaks in previously unaffected temperate regions such as Northern Europe. The emergence of new BTV serotypes has further complicated disease control.

Efforts to control Bluetongue focus on vaccination, vector control, and movement restrictions. Several inactivated and live attenuated vaccines exist, but their effectiveness depends on the circulating BTV serotype. Novel mRNA and recombinant vaccines are under development to provide broader protection. Vector control strategies include insecticide applications, habitat modifications, and midge repellents. Strict surveillance programs help detect and contain outbreaks, but challenges remain in regions with high midge populations and cross-border livestock trade.

Despite ongoing control measures, Bluetongue remains a major challenge for livestock industries worldwide. Continued research into climate-adaptive strategies, improved vaccines, and vector management is essential to mitigate its impact and protect animal health.
Bluetongue disease

Bovine viral diarrhea (BVD)

The disease is caused by the Bovine Viral Diarrhea Virus (BVDV). The virus is widespread and most herds are at risk for infection. It is a worldwide disease that causes mild fever, diarrhea and leukopenia but may also cause fatal hemorrhagic diarrhea.

Infection leads to immunosuppression and can cause signs in multiple body systems in addition to the digestive tract.

Clinical disease associated with BVD virus infection is most common in young cattle (6–24 months old). The clinical presentation can range from inapparent or subclinical infection to acute and severe enteric disease.

BVD is transmitted in a number of ways. Either through a congenital infection of the fetus or after birth. Cattle that are acutely or persistently infected with BVD virus shed the virus in nasal and oral secretions, urine and feces. The virus gains entrance through mucosal membranes and replicated in the epithelial cells. The virus spreads systemically throughout the blood stream, both as free virus in the serum and in infected leukocytes.

It is possible for cattle to become infected via contact with contaminated fomites, such as water buckets, calf feeders, feed bunks, IV equipment, nose leads, clothing or people and cattle trucks.

The incubation period is about three to five days. Signs of acute infection include fever, lethargy, loss of appetite, ocular discharge, nasal discharge oral lesions, and diarrhea. Chronic infection may lead to signs of mucosal disease. Sores or ulceration in the mouth and gums may be present, along with reduced milk production in cows.

The importance of BVD in reproduction is that the virus crosses the placenta and causes intrauterine infections leading to early embryonic death, abortion, congenital defects or persistently infected calves. BVD has been implicated in 2-7% of dairy cattle abortions but has no permanent effect on fertility. Some infected animals may die, while others will recover, usually within one or two weeks.

If pregnant animals recover, they may abort about 2 to 4 weeks after exposure, especially if they are in the second trimester of pregnancy.

Vaccination is routinely practiced for BVD due to the economic impact of the disease in beef and dairy production. Modified live virus (MLV) vaccines can provide reproductive duration of immunity.
Bovine viral diarrhea (BVD)

Brucellosis disease

The disease is also known as contagious abortion or Bang's disease. It is a contagious, costly disease of ruminant such as cattle.

Brucellosis is a zoonotic disease of great animal welfare and economic implications worldwide known since ancient times. The disease is caused by a group of bacteria known scientifically as the genus Brucella. Three species of Brucella cause the most concern: B. abortus, principally affecting cattle, bison and cervids; B. suis, principally affecting swine and reindeer but also cattle and bison; and B. melitensis, principally affecting goats but not present in the United States.

Each species of Brucella tends to be associated with a specific host, but other animals can be infected, especially when they are in close contact. Cattle are the usual hosts for Brucella abortus. This organism also causes brucellosis in bison, water buffalo, camels and elk, and occasionally affects other species.

Mixed farming of cows, buffaloes, sheep and goats has increased the risk of brucellosis where small ruminants act as primary hosts for B. melitensis and cattle as spillover host.

Brucellosis is a widespread reproductive disease, commonly causing abortion, death of young ones, stillbirth, retained placenta or birth of weak calves, delayed calving, male infertility, and marked reduction in milk yield.

The bacteria infect reproductive tissues, lymph nodes, and the spleen, and therefore cause inflammation, edema, and necrosis. In pregnant animals it causes placental lesions and increases the risks of abortion.
Brucellosis disease

Black quarter disease

Black quarter (synonym: blackleg, quarter ill, quarter evil, symptomatic anthrax, or emphysematous gangrene) is an acute infectious disease of cattle. It is the second most important bacterial disease next only to hemorrhagic septicemia in causing death among bovids.

The disease usually commences in skeletal muscles but occasionally the heart or diaphragm is affected. The primary site of infection of black quarter was myocardium. The most commonly reported findings in classical blackleg are acute neutrophil necrotizing myositis that affects the skeletal muscle, and visceral myonecrosis, which is rarely diagnosed, but can affect the heart, sublingual muscles, and diaphragm.

Black quarter (BQ) is a predominant disease of cattle but traumatic black quarter may be seen in other animals.

Most cases of Black quarter occur during the warm months, or after soil excavation, or during very high annual rainfall that can expose and activate latent spores. In addition, the disease is enzootic in areas with a history of flooding.

Black quarter disease is caused by Clostridium chauvoei – a Gram-positive, rod shaped, sporeforming and toxin-producing anaerobe. The spores of the bacterium are very resistant to adverse environmental stress. There is no consensus on the pathogenesis of black quarter but toxins and neuraminidase produced by the causative bacteria are believed to play a significant role.
Black quarter disease

Mad cow disease

Mad cow disease is the common name for Bovine Spongiform Encephalopathy (BSE), a fatal infectious disease of the brain and spinal cord in cows that causes microscopic holes in brain tissue.

Spongiform encephalopathy is a progressive neurological disorder of cattle and thought to be caused by tiny particles called prions.

Mad cow disease is the bovine form of a condition that began appearing in British cows in the 1980s. Some were pathologically nervous, others bizarrely aggressive, but when the “mad cows” died, as they inevitably did, their brain were discovered to be shot through with holes.

The first confirmed case among US cattle occurred in December 23. Canada’s first case emerged in May 2003, prompting the US to stop Canadian beef imports.

Most cattle are infected when they ingest (oral) prion contaminated “ruminant” meat and bone meal contaminated with prions.

Bovine Spongiform Encephalopathy is typically a slow developing disease. Infected cattle appear normal for 2 to 8 years. As the disease develops, the brain is affected. Signs such as trembling, stumbling, swaying and behavioral changes (e.g., nervousness, aggression or frenzy) are seen. The disease causes damage to the brain cells which take on a sponge-like appearance. This physical damage results in loss of coordination, dementia, and, eventually death.
Mad cow disease

Normal cow

Foot and mouth disease in cattle

Foot and mouth disease is a highly contagious viral vesicular disease of cloven-hoofed animals.  Foot and mouth disease virus is the prototype member of the Aphthovirus genus of the family Picornaviridae.

Although seldom lethal in adult animals, it causes serious production losses and is a major constraint to international trade in livestock and livestock products.

Foot and mouth disease spreads mots rapidly during the summer months because of the greater traffic in animals then.

Foot and mouth disease is most commonly associated with movement of infected animals and their contact with susceptible animals.

During the early stages of disease, infected animals shed virus in all their excretions and secretions, including their breath. The disease is characterized by depression, fever, and the appearance of vesicles filled with clear fluid in certain mucous membranes and portions of the skin.

The essential pathological change in the tongue is necrosis of epithelial cells in the stratum spinosum, intracellular edema and granulocytic infiltration.

The disease is endemic and at a high prevalence in many countries in Africa, the Middle East and Asia and is also present in parts of South America.
Foot and mouth disease in cattle