Caseous lymphadenitis (CLA) is an

infectious disease An infection is the invasion of tissue (biology), tissues by pathogens, their multiplication, and the reaction of host (biology), host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmis ...

caused by the bacterium ''

Corynebacterium pseudotuberculosis ''Corynebacterium pseudotuberculosis'' is a Gram-positive bacterium known to infect ruminants, horses, and – rarely – people. It is a facultative anaerobic organism that is catalase-positive and capable of beta-hemolysis. In small ruminants, ...

'', that affects the

lymphatic system The lymphatic system, or lymphoid system, is an organ system in vertebrates that is part of the immune system and complementary to the circulatory system. It consists of a large network of lymphatic vessels, lymph nodes, lymphoid organs, lympha ...

, resulting in abscesses in the lymph nodes and

internal organs In a multicellular organism, an organ is a collection of tissues joined in a structural unit to serve a common function. In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to a ...

. It is found mostly in

goats The goat or domestic goat (''Capra hircus'') is a species of goat-antelope that is mostly kept as livestock. It was domesticated from the wild goat (''C. aegagrus'') of Southwest Asia and Eastern Europe. The goat is a member of the famil ...

and

sheep Sheep (: sheep) or domestic sheep (''Ovis aries'') are a domesticated, ruminant mammal typically kept as livestock. Although the term ''sheep'' can apply to other species in the genus '' Ovis'', in everyday usage it almost always refers to d ...

and at the moment it has no

cure A cure is a substance or procedure that resolves a medical condition. This may include a medication, a surgery, surgical operation, a lifestyle change, or even a philosophical shift that alleviates a person's suffering or achieves a state of heali ...

Research

This disease is widely distributed throughout the world. It is found in

North North is one of the four compass points or cardinal directions. It is the opposite of south and is perpendicular to east and west. ''North'' is a noun, adjective, or adverb indicating Direction (geometry), direction or geography. Etymology T ...

and

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...

and

Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...

. Caseous lymphadenitis causes considerable economic harm, because skins and carcasses have to be condemned. It seriously affects reproduction efficiency,

wool Wool is the textile fiber obtained from sheep and other mammals, especially goats, rabbits, and camelids. The term may also refer to inorganic materials, such as mineral wool and glass wool, that have some properties similar to animal w ...

meat Meat is animal Tissue (biology), tissue, often muscle, that is eaten as food. Humans have hunted and farmed other animals for meat since prehistory. The Neolithic Revolution allowed the domestication of vertebrates, including chickens, sheep, ...

and milk production. Particularly in Australia, one of the largest producers of meat and wool. Studies have found CL incidence in commercial goat herds as high as 30%.

Cause

The causative organism of caseous lymphadenitis is ''Corynebacterium pseudotuberculosis''. Once successfully established within the host, this

pathogen In biology, a pathogen (, "suffering", "passion" and , "producer of"), in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a Germ theory of d ...

will circumvent the

immune system The immune system is a network of biological systems that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to bacteria, as well as Tumor immunology, cancer cells, Parasitic worm, parasitic ...

with ease. As a result, it causes chronic infection that may last for most or all of an animal's life, although it is seldom lethal.

Signs

It manifests itself predominantly in the form of large,

pus Pus is an exudate, typically white-yellow, yellow, or yellow-brown, formed at the site of inflammation during infections, regardless of cause. An accumulation of pus in an enclosed tissue space is known as an abscess, whereas a visible collect ...

-filled

cysts A cyst is a closed Wikt:sac, sac, having a distinct Cell envelope, envelope and cell division, division compared with the nearby Biological tissue, tissue. Hence, it is a cluster of Cell (biology), cells that have grouped together to form a sac ...

on the neck, sides and udders of goats and sheep. Abscesses can also develop on internal organs. An abscess can develop either at the location where the bacteria enters the body or at a nearby

lymph node A lymph node, or lymph gland, is a kidney-shaped organ of the lymphatic system and the adaptive immune system. A large number of lymph nodes are linked throughout the body by the lymphatic vessels. They are major sites of lymphocytes that includ ...

. The infection can spread through the blood or lymphatic system, causing abscesses to form in other lymph nodes or internal organs throughout the body. Most commonly affected organs are the

liver The liver is a major metabolic organ (anatomy), organ exclusively found in vertebrates, which performs many essential biological Function (biology), functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of var ...

lung The lungs are the primary Organ (biology), organs of the respiratory system in many animals, including humans. In mammals and most other tetrapods, two lungs are located near the Vertebral column, backbone on either side of the heart. Their ...

kidney In humans, the kidneys are two reddish-brown bean-shaped blood-filtering organ (anatomy), organs that are a multilobar, multipapillary form of mammalian kidneys, usually without signs of external lobulation. They are located on the left and rig ...

s and lymph nodes associated these organs. Abscesses grow gradually over time, and if they are located close to the skin, rupture is common. The abscesses are reported not to be painful.

Pathogenesis and transmission

The disease is highly contagious. When abscess rupture, releases it huge numbers of bacteria onto the skin and wool and it results to the consequent contamination of the surrounding environment. Neighboring animals may then be infected by the bacteria through immediate physical contact with the affected individual or indirectly via already contaminated fomites. Infected animals can contaminate the feed, water, soil, pasture and facilities. Even away from its mammalian host, the organism is well equipped for long-term survival in the environment. The disease is also easily spread through the materials that are used during the operation of the animals such as

castration Castration is any action, surgery, surgical, chemical substance, chemical, or otherwise, by which a male loses use of the testicles: the male gonad. Surgical castration is bilateral orchiectomy (excision of both testicles), while chemical cas ...

, identification with ear tags or by tattooing, and dehydration of abscesses. It is thought to also be spread by coughing or even by

flies Flies are insects of the Order (biology), order Diptera, the name being derived from the Ancient Greek, Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwin ...

Diagnostics

Culture remains the gold standard for diagnosis in small ruminants. Synergistic hemolysis inhibition testing, as done for equine species has the ability to generate false positive results when applied to small ruminants.

Occurrence in other species

''Corynebacterium pseudotuberculosis'' has also been isolated from occurring in other species such as

deer A deer (: deer) or true deer is a hoofed ruminant ungulate of the family Cervidae (informally the deer family). Cervidae is divided into subfamilies Cervinae (which includes, among others, muntjac, elk (wapiti), red deer, and fallow deer) ...

cattle Cattle (''Bos taurus'') are large, domesticated, bovid ungulates widely kept as livestock. They are prominent modern members of the subfamily Bovinae and the most widespread species of the genus '' Bos''. Mature female cattle are calle ...

pig The pig (''Sus domesticus''), also called swine (: swine) or hog, is an omnivorous, domesticated, even-toed, hoofed mammal. It is named the domestic pig when distinguishing it from other members of the genus '' Sus''. Some authorities cons ...

hedgehog A hedgehog is a spiny mammal of the subfamily Erinaceinae, in the eulipotyphlan family Erinaceidae. There are 17 species of hedgehog in five genera found throughout parts of Europe, Asia, and Africa, and in New Zealand by introduction. The ...

laboratory mice The laboratory mouse or lab mouse is a small mammal of the order Rodentia which is bred and used for scientific research or feeders for certain pets. Laboratory animal sources for these mice are usually of the species ''Mus musculus''. They a ...

camel A camel (from and () from Ancient Semitic: ''gāmāl'') is an even-toed ungulate in the genus ''Camelus'' that bears distinctive fatty deposits known as "humps" on its back. Camels have long been domesticated and, as livestock, they provid ...

horse The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 mi ...

s, and humans. In only three species; sheep, goats and horses, it is recognized as a specific disease syndrome. The biotype of ''Corynebacterium pseudotuberculosis'' affecting horses and cattle is distinguishable from the biotype that infects small ruminants based on its ability to reduce nitrate

in vitro ''In vitro'' (meaning ''in glass'', or ''in the glass'') Research, studies are performed with Cell (biology), cells or biological molecules outside their normal biological context. Colloquially called "test-tube experiments", these studies in ...

. The equine and bovine strains can reduce nitrate, whereas the small ruminant strains typically do not.

Treatment and vaccination

Treatment of affected animals consists of the drainage of abscesses, followed by cleansing and chemical cauterization, usually with 10%

iodine Iodine is a chemical element; it has symbol I and atomic number 53. The heaviest of the stable halogens, it exists at standard conditions as a semi-lustrous, non-metallic solid that melts to form a deep violet liquid at , and boils to a vi ...

, or even removal of the affected superficial lymph nodes. Also there is antibiotic therapy, which can be used as a treatment. Despite the fact that ''C. pseudotuberculosis'' is sensitive in vitro to almost all antibiotics that have been tested, antibiotic therapy is not very efficient. The most effective way of controlling caseous lymphadenitis is still a topic of discussion. Vaccination is the primary remedy for the control of the disease in several countries, whereby immunisation reduces the spread of infection, leading to a gradual decline in incidence of the disease. However, proprietary caseous lymphadenitis vaccine is still not available, which would be a complete protection against the disease.

References

{{Commons category, Caseous lymphadenitis Sheep and goat diseases