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Toxemia and endotoxemia

Toxemia is a clinical systemic state caused by widespread activation of host defense
mechanisms to the presence of toxins produced by bacteria or injury to tissue cells.

Toxemia does not include the diseases caused by toxic substances produced by

plants or insects or ingested organic or inorganic poisons.

Theoretically, a diagnosis of toxemia can be made only if toxins are demonstrable in the bloodstream.

The most common form of toxemia in large animals is endotoxemia, caused by

the presence of lipopolysaccharide cell wall components of Gram-negative
bacteria in the blood, and characterized clinically by abnormalities of many body
systems.

Gram-negative bacteria such as E. coli, Salmonella spp., Pasteurella spp. And Histophilus somni, as examples, cause many diseases of ruminants in which
endotoxemia is common

The abnormalities of endotoxemia include:

Marked alterations in cardiopulmonary function.
Abnormalities in the leukon (neutropenia and lymphopenia) and thrombocytopenia that may lead to coagulopathies.
Increased vascular permeability.
Decreased organ blood flow and metabolism, leading to heart and renal failure.
Decreased gastrointestinal motility.
Decreased perfusion of peripheral tissues, leading to shock.
The need for intensive and complex therapy.
A high case fatality rate.


ETIOLOGY OF TOXEMIA AND ENDOTOXEMIA

Toxins can be classified as antigenic or metabolic.

Antigenic toxins:
These are produced by bacteria and to a lesser extent by helminths. Both groups of
pathogens act as antigens and stimulate the development of antibodies. Antigenic
toxins are divided into exotoxins and endotoxins.

Exotoxins

These are protein substances produced by bacteria that diffuse into the surrounding
medium. They are specific in their pharmacological effects and in the antibodies
that they induce. The important bacterial exotoxins are those produced by Clostridium spp.

They may be ingested preformed, as in botulism, or produced in large quantities by
Heavy growth in the intestines, such as in enterotoxemia, or from growth in tissue,
as in blackleg and black disease.

Enterotoxins

These are exotoxins that exert their effect principally on the mucosa of the intestine,
causing disturbances of fluid and electrolyte balance. The most typical example is
the enterotoxin released by enterotoxigenic E. coli, which causes a hypersecretory
diarrhea in neonatal farm animals.

Endotoxins

The endotoxins are lipopolysaccharides found in the outer wall of the bacteria. Endotoxins are released into the immediate surroundings when the bacteria undergo rapid proliferation with production of unused sections of bacterial cell wall or, most commonly, when the bacterial cell wall breaks.

Endotoxin gains access to the blood when there is a severe localized infection, such as a coliform mastitis in dairy cattle

Gram-negative bacteria are present in the intestinal tract as part of the normal microflora and endotoxins are also present. The endotoxins are not ordinarily
absorbed through the intestinal mucosa unless it is injured, as in enteritis or more
particularly in acute intestinal obstruction.

Notes

Ordinarily, small amounts of endotoxin that are absorbed into the circulation are detoxified in the liver but, if hepatic efficiency is reduced or the amounts of toxin are large, a state of endotoxemia is produced.

Endotoxins may also be absorbed in large amounts from sites other than intestine including the mammary gland, peritoneum, abscesses and other septic foci, or from large areas of injured or traumatized tissue.


OR
Varying degrees of severity of toxemia occur in diseases such as mastitis, peritonitis, pneumonia and pleuritis, pericarditis, septic metritis, septicemia of neonates, myositis, meningoencephalitis and some enteritides

Examples:

The best known endotoxins are those of E. coli and Salmonella spp.

The most common causes of endotoxemia in horses are associated with diseases of the gastrointestinal tract including colitis, intestinal strangulation or obstruction and ileus.

Metabolic toxins

These may accumulate as a result of incomplete elimination of toxic materials normally produced by body metabolism, or by abnormal metabolism. Normally, toxic products produced in the alimentary tract or tissues are excreted in the urine and feces or detoxified in the plasma and liver.

When these normal mechanisms are disrupted, particularly in hepatic dysfunction,

the toxins may accumulate beyond a critical point and the syndrome of toxemia appears.

In obstruction of the lower alimentary tract there may be increased absorption of toxic phenols, cresols and amines that are normally excreted with the feces, resulting in the development of the syndrome of autointoxication.