Caseous lymphadenitis (CLA) is an

infectious disease An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable di ...

caused by the bacterium '' Corynebacterium pseudotuberculosis'', that affects the lymphatic system, resulting in abscesses in the lymph nodes and

internal organs In biology, 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 act together in a ...

. It is found mostly in

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

and

sheep Sheep or domestic sheep (''Ovis aries'') are domesticated, ruminant mammals 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 domesticated ...

and at the moment it has no cure.

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 or geography. Etymology The word ''north ...

and

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sout ...

, Australia,

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located entirel ...

Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an are ...

and

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

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

wool Wool is the textile fibre 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 properties similar to animal wool. ...

, meat 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 ( el, πάθος, "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 ...

will circumvent the

immune system The immune system is a network of biological processes that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as cancer cells and objects such as wood splint ...

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 bacterial or fungal infection. An accumulation of pus in an enclosed tissue space is known as an abscess, whereas a visible collection ...

-filled

cysts A cyst is a closed sac, having a distinct envelope and division compared with the nearby tissue. Hence, it is a cluster of cells that have grouped together to form a sac (like the manner in which water molecules group together to form a bubble) ...

on the neck, sides and

udders An udder is an organ formed of two or four mammary glands on the females of dairy animals and ruminants such as cattle, goats, and sheep. An udder is equivalent to the breast in primates and elephantine pachyderms. The udder is a single mass ha ...

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. 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 organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it ...

, lungs,

kidney The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; blo ...

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, surgical, chemical, or otherwise, by which an individual loses use of the testicles: the male gonad. Surgical castration is bilateral orchiectomy (excision of both testicles), while chemical castration uses pharma ...

, identification with

ear tag An ear tag is a plastic or metal object used for identification of domestic livestock and other animals. If the ear tag uses Radio Frequency Identification Device ( RFID) technology it is referred to as an electronic ear tag. Electronic ear ta ...

s 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 Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced m ...

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 such as

deer Deer or true deer are hoofed ruminant mammals forming the family Cervidae. The two main groups of deer are the Cervinae, including the muntjac, the elk (wapiti), the red deer, and the fallow deer; and the Capreolinae, including the re ...

cattle Cattle (''Bos taurus'') are large, domesticated, cloven-hooved, herbivores. They are a prominent modern member of the subfamily Bovinae and the most widespread species of the genus ''Bos''. Adult females are referred to as cows and adult ma ...

pig The pig (''Sus domesticus''), often called swine, hog, or domestic pig when distinguishing from other members of the genus '' Sus'', is an omnivorous, domesticated, even-toed, hoofed mammal. It is variously considered a subspecies of ''Sus ...

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

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 mice are usually of the species ''Mus musculus''. They are the most commonly used ...

, camels,

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 million yea ...

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'') studies are performed with microorganisms, cells, or biological molecules outside their normal biological context. Colloquially called " test-tube experiments", these studies in biology ...

. 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, 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