Out West Mfg.
Clostridial species which cause disease in cattle, sheep, goats, swine,
Information supplied from Schering-Plough Animal Health Corp. information booklet, Clostridials, (SPAH-BOV-94)
Page 1 of 4
The information, which follows, puts into perspective a modern view of the clostridial diseases called the infection site concept. Although much of the information presented is elementary, it is hoped that the reader will accept it as necessary to give this concept proper relevance.
Clostridial Species Which Cause Disease in Livestock
The genus Clostridium contains many different species and species types. Thirty-six are listed in a highly regarded reference. (The Pathogenic Anaerobic Bacteria, Second Edition L.D.S. Smith). Of these, eleven (worldwide basis) have been shown to be pathogenic for livestock and of economic importance. They are: Cl. chauvoei, Cl. septicum, Cl. Sordellii, Cl. novyi Type A, Cl. novyi Type B, Cl. novyi Type D (Cl. haemolyticum), Cl. perfringens Type A, Cl. perfringens Type B, Cl. perfringens Type C, Cl. perfringens Type D, and Cl. tetani.
While diseases produced by clostridia have been recognized for many centuries, it was not until the late nineteenth century that the individual species were isolated and identified. The chronology of this activity is as follows: Cl. tetani, 1889; Cl. novyi, Type B, 1894; Cl. perfringens, 1892, Cl. botulinum, 1896; Cl sordellii, 1922; Cl. haemolyticum (Cl. novyi Type D), 1926.
The diseases caused by these organisms have, because of their severe and highly fatal nature, been the subjects of considerable investigation. These studies have been generally directed toward the development of control measures for the individual diseases. As a consequence, much has been learned concerning the disease caused by the different agents. A unified concept, based on common features such as principle infection sites and pathogeneses shared by the different agents, has not, however, been developed to aid in better understanding this disease complex and in establishing control programs.
Bacteria of the genus Clostridium possess certain unusual characteristics, which distinguish them from other types. Three principal such characteristics are: (1) the ability to multiply only in the absence of oxygen (anaerobic environment) (2) the ability to survive adverse conditions by transforming into highly resistant form called spores, and (3) the release of potent toxins during the process of multiplying.
It is the combination of these characteristics that makes the clostridia unique and highly dangerous.
In their spore form, clostridia are able to exist in the presence of oxygen----in the soil, on body surfaces and within the healthy animal. The spore form is highly resistant to the forces of nature----drying, temperature changes and prolonged separation from energy supplies. Meanwhile, they retain the ability to begin multiplying when favorable conditions occur. In many repects, they are similar to seed produced by plants that remain in the soil without growing until conditions favorable for germination occur.
When a suitable anaerobic environment develops in the immediate vicinity of a clostridial spore, it can activate (germinate) and transform into a vegetative bacterial cell which then begins to multiply. During this multiplication, potent toxins are released.
A number of different toxins are released by the multiplying cells. The actual types vary by clostridial species. Of greatest importance are those that destroy tissue cells (necrotizing) and red blood cells (hemolyzing), and those that interrupt nerve impulses (neurotoxins).
In the living animal, anaerobic conditions are established when the normal blood supply to a particular tissue site is interrupted or when changes occur in the digestive process of the intestinal tract. The interruption of blood supply occurs as the result of tissue damage, the origin of which varies considerably. If a clostridial spore is present in the damaged tissue, it germinates and transforms into the vegetative form. Multiplication and toxin production follow. The necrotizing toxins expand the area of the cell death, perpetuation the anaerobic environment. As the process advances and more toxins are released, these are carried by the bloodstream to the other parts of the body, resulting in widespread destruction of cells, disruption of organ function and rapid death of the animal.
Spores that germinate in the intestinal tract give rise to cells which release toxins that cause lesions of the intestinal wall and/or which are absorbed from the intestine into the bloodstream, to produce death through effects on other tissues and organ function.
Not all pathogenic species of Clostridium cause disease in all animal species. Further, there are variations in the degree of pathogenicity. These factors are expressed in the chart below (worldwide basis):
Susceptibility of Animals to Clostridial Disease
The clostridia present problems for the diagnostician, whether in the field or in the laboratory.
The different species have both unique and common characteristics. For Example, Cl. Chauvoei, Cl. Septicum and Cl. Sordellii produce similar pathology, yet are quite different in staining reactions and toxin production. Cl. Novyi Types B and D, and Cl. Perfringens Types B, C and D share some somatic and toxin characteristics.
Field diagnosis based on clinical signs is seldom possible. This is primarily because animals are usually found dead. Diagnosis, therefore, must be based on postmortem examination and laboratory studies. Usually, sufficient time has elapsed since death for tissue to deteriorate (autolyze). Under these conditions, differential diagnosis may not be possible.
Laboratory diagnosis is complicated by the fact that specimens may contain, in addition to the causative agent, many other types of bacteria (both aerobes and anaerobes) which were resident in the diseased animal. Because certain of these bacteria may grow more readily than the causative agent, they may be the only types isolated in the laboratory. This can lead to mistaken conclusions as too the agent responsible for death of the animal. Further, efforts to detect lethal toxins are often unsuccessful due to their rapid breakdown.
Efforts to control clostridial diseases of livestock actually preceded the identification of a causative organism. The first known vaccine, consisting of processed, dried fluid from blackleg lesions, dates back to 1881. The causative agent for blackleg was not identified until 1887.
Since that time, control efforts have in general followed the development of immunizing agents. For example, univalent Cl. Chauvoei bacterin was used exclusively until evidence emerged that Cl. Septicum was also a serious threat. The two organisms were then combined in a product that gained widespread use.
Over the ensuing years, all clostridia presently known to be responsible
for diseases of economic significance have been incorporated in vaccines.
They are available in numerous combinations and, in general, are used
as the need for protection is viewed subjectively on a local basis (often
on an operation-to-operation basis).
An upsurge in clostridial disease research began developing in the 1960s. The chief institution involved was Wellcome Research Laboratories, Kansas City, later known as Schering-Plough Animal Health Corp. Intense work was undertaken into disease-protection relationships and the role of advanced culturing technology in product development.
By the early 1970s, numerous advanced products, such as Electroid® 7, had been developed. Their use in the field followed the historical approach-subjectively perceived need based on the individual diseases. It was apparent, however, that the lack of certain information had become a barrier to the development and proper evaluation of more effective control measures. The deficiencies related to: (1) factors responsible for initiating active infections; (2) factors in the pathogenesis of disease, which result in such rapid death.
A major program of investigation was launched to define the clinical and pathological characteristics of clostridial diseases in cattle and sheep and to develop a more systematic approach to their control. Evolving from these investigations was the concept that different groups of clostridial diseases occur as the result of predilection of different groups of agents for certain tissue sites.
The principal infection sites of the species which commonly affect livestock were shown to be the following:
Principal Infection Sites of Clostridial Species of Current Economic Concern In Livestock In The U.S.A.
The need for preinfection immunizations is of critical importance in controlling all clostridial diseases. This is true for the following reasons: (1) Clostridial spores reside within the animal body and are widely distributed in the soil; (2) the presence of spores within the animal does not stimulate immunity to the vegetative forms of the organism or to the toxins they release; (3) activated clostridia produce death before an adequate defense response can be mounted.
Because protective antibodies must be immediately available to combat the active, toxin-releasing infection, two doses of vaccine are required for assurance of protection against all clostridial agents except Cl. Chauvoei, which produces the least amount of toxin. The second dose stimulates a secondary (anamnestic) response which results in much higher and longer lasting antibody levels than those resulting from only a single dose. In this respect, immunization against clostridial diseases differs from other diseases such as IBR or leptospirosis. In the latter, the disease process develops more slowly following field infection, thus enabling the secondary immune response to occur before the acute stage is reached.
There are variations in the immunizing value of the different fractions of the bacterial cells (somatic antigens) and their toxins. This has been studied extensively and sophisticated ultrafiltration processes have been developed to promote the production of appropriate elements. The relative importance of these components is expressed in the table below:
Antigenic Components of Certain Pathogenic Clostridia and Their Relative Value in Immunization
Out West Mfg.