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In this chapter an overview of some important gram-positive organisms that are significant to the health of domestic animals will be discussed. This will include anthrax, the Corynebacteriaceae group, and finally the Erysipelothrix group. Anthrax is a natural disease of domestic animals and wild animals, which includes mammals, birds, and reptiles. Bacillus anthraces a gram-positive spore forming immotile rod is the causative agent. The disease is characterized by an acute fever, enlarged, black , soft spleen, edema and hemorrhage of body tissue. Anthrax is world wide distributed. Particularly where no organized control of animal disease exist. However, anthrax may be prevalent in some area of the USA called "Anthrax Districts" in such states as Louisiana, Texas, California and Nebraska.
Anthrax is not usually transmitted directly from one subject to the other. After swarming in the tissues of the affected animal the organism is eliminated in the secretions and excretions at short time prior to death. The organism may then be distributed in a number of ways including birds, floods, hay or grass harvested earlier from the contaminated area and flies of the blood sucking variety. The majority of the outbreaks have been from contaminated feedstuff. Generally anthrax is very explosive in nature and disease is usually characterized by sudden onset and a rapidly fatal course. Anthrax is a reportable disease in most states. It requires quarantine on premises, regulation of immuning agents and disinfection of the transporting car and truck.
The Corynebacteriaceae are ubiquitous group of gram-positive organisms rods that usually demonstrates the characteristic palisade arrangement. For the most part these are clubbed shaped organisms and pleomorphism is common. The corynebacteria are numerous on the surface of mucous membranes where most are part of the normal flora and are after referred to as "diptheroids". This term denotes the harmless sporophyte rather than one of the recognized pathogens. However, some species are important as pathogens for domesticated animals such as C. equi, C. ouis, C. pyogenes and C. renale. These organisms will be discussed more fully in the chapter.
Another important gram-positive organism of significant economic importance to the animal industry is Listeria monocytogenes. This organism causes a disease called listeriosis which is characterized by meningo-encephalitis, abortion or septicemia. L. monocytogenes is a member of the Corynebacteriaceae, a diphtheroid-like bacilli and usually occurs in pairs. The most prevalent form of the listeriosis in ruminant is encephalitis which is the form of greatest economic importance. The organism affects animals of all ages, sexes and usually they are the best animals in the herd. Listeria infection has public health significance since the organism has been isolated from milk of cattle following abortion and some cases of mastitis. In such cases milk is a hazard because the organism may endue certain forms of pasteurization and thus infect humans who drink the milk either raw or improperly pasteurized. The organism infects sheep but swine to a lesser extent.
Erysipelothrix insidiosa another important gram-positive organism is also a member of the Corynebacteriaceae group. The organism can be isolated from clinical specimens of a variety of mammalian species and birds. Most importantly it is responsible for the erysipelas of the swine and turkeys, and erysipeloid of man. the organism is an important cause of endocarditis in swine. The disease may exist in three different forms including the endocarditis, arthritis and the cutaneous form.
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26.3.1.1 Definition:
Anthrax is an acute febrile disease of mammals caused by Bacillus anthraces and characterized by an enlarged, black, soft spleen, edema and hemorrhage of subcutaneous and subserous tissues.
Synonyms: Splenic fever, charbon
History:
26.3.1.2.1 Bacillus anthraces
is unique since it is the only aerobic sporulating species. The anthrax is a large, straight, square-ended rod usually about 1 micron in diameter and 3-6 microns long. It forms long filaments in culture media, but filaments are never seen in tissues. The organism is encapsulated. The capsules are well marked and can be stained rather easily. In the presence of air, abundant spores are formed. Because of lack of air or sufficient oxygen, spores are not formed in the blood and internal organs. It is not acid-fast, but stains easily with all of the usual dyes and is Gram-positive.
26.3.1.2.2 Occurrence and Distribution
Anthrax is found all over the world. It is particularly prevalent in countries where no organized control of animal disease exists. India, China, Siberia, Russia, North America and Mexico and some parts of South America have anthrax as a major problem. In the USA, there are areas in California, Nebraska, Texas and Louisiana that are classified as "Anthrax Districts".
Spores are transmitted from one area to the other, even from one country to another, through contaminated products such as hides, wool, bone meal, fertilizer or plants such as hay. Carnivores may transmit anthrax, and for a number of years the turkey buzzard has been incriminated as a spreader. Biting flies have been known to transmit anthrax. The majority of outbreaks have been due to contamination of feed stuffs.
26.3.1.2.3 Etiology
26.3.1.2.4 Behavior:
The anthrax organism grows readily on the simplest organic infusion medium. Best growth occurs on solid media exposed to air. Growth is meager under anaerobic conditions. The organism develops into characteristic "ground glass" surface colonies on agar plates. Under low magnification the margins of these colonies appear irregular and resemble locks of wavy hair. It is for this reason that they are sometimes described as "Medusa-head colonies". This is thought to be due to the habits of the bacilli of forming long filaments in chains that lie parallel. Gelatin is liquefied, milk is rendered acid and a soft curd usually is formed. The organism grows readily on the cut surface of many boiled vegetables such as potatoes, beets, pod of string beans, carrots or on the cut surface of a banana. Sporulation occurs early and profusely on these substances. Acid but no gas is produced in glucose, sucrose, maltose and salicin, Figure 22 and 23.
26.3.1.2.5 Resistance:
Growing forms of the anthrax bacillus are only slightly resistant. It is easily killed by ordinary disinfectants, by pasteurization, and quickly succumbs to the action of putrefactive bacteria. Under aerobic conditions spores are readily formed. In the organ of an animal dead of anthrax, the oxygen supply is insufficient for spore formation. If the carcass is opened, the tissues are exposed to air, and then the organisms are able to sporulate so that resistance is generally enhanced.
The spores resist dying for long periods of time. Spores surviving for 10 or more years have been recorded. A 10-minute exposure to boiling water is enough to destroy some strains; therefore, anthrax spores are not so resistant to heat as is commonly supposed. At 1200C, dry heat, it is necessary to expose anthrax spores for an hour to kill them all. Sanitizing burlap feed bags contaminated with anthrax spores can be accomplished by exposing them to dielectric heat at 112.70C for 30 minutes.
26.3.1.2.6 Transmission:
Anthrax is not usually transmitted directly from one individual to another. The organism swarms in the tissue of the affected animal and is eliminated in the secretions and excretions a short time prior to death. Birds or animals of prey devouring a carcass, or an animal carelessly autopsied in the field may scatter the organism in the soil. The organism may be scattered by floods. Animals may contract the disease in winter by feeding on hay or grass harvested earlier from anthrax-contaminated areas. In hot climates where flies are abundant, the disease is transmitted by the blood-sucking varieties, notably by the large horseflies of the genus, Tabanus.
26.3.1.2.7 Clinical Picture
Bacillus anthraces is pathogenic for cattle, sheep (except Algerian), horses, mules, etc. Anthrax appears as a septicemia in the first four species of animals in an apoplectic form, an acute form and a subacute form. A more or less chronic form is seen in sheep surviving the disease, though it may be found in all species of animals affected. Generally, anthrax is very explosive in nature. The disease is usually characterized by sudden onset and a rapidly fatal course. Some animals in a herd are found dead without having previously shown any evidence of a disease.
In the acute form, the first noticeable sign is a rise in temperature to about 104-1080F. This is followed by excitement, and cows affected will sometimes charge the attendant. The excitement stage is followed by depression, respiratory distress, trembling staggers, convulsions, and death. There is a rumen stasis and a great reduction in the amount of milk produced. One of the most important features in fatal cases is the bloody discharge from the natural openings, particularly the anus.
26.3.1.2.8 Pathogenesis
The manifestation of the disease is influenced by the manner of infection. If it occurs through the internal organs (no visible evidence of a localization) it is characterized by a sudden onset and a rapidly fatal course. The peracute form may sometimes occur in herbivores; may terminate fatally in 1-2 hours. The acute form is fatal in less than 24 hours. The organism may be found in the excretion or the blood in fairly large numbers at the time of death. Identification in these films is therefore the simplest and most certain way of making an adequate diagnosis. The localized form of anthrax which occurs more often in man than the domestic animals is seen when infection has occurred through a wound in the skin. Cutaneous anthrax takes the form of a swelling of an edematous nature which is hot and painful at first, but later becomes cold and painless. This type of anthrax is called malignant carbuncles in man. Anthrax in cattle, sheep and horses usually appears in the spring and summer months. Most infection results from sneezing on infected pastures. The cases usually are acute, and most of them are fatal.
Death of the animal results from the effects of the extracellular toxic complex released by the organism. The toxic complex consists of three components (Factor I, edema factor; Factor II, protective antigen; and Factor III, lethal factor). The chemical nature and biologic significance of each of these is shown in Table 1 and 2. These factors operate in combination and have little or no toxic action as single entities. Their total effect is to damage and kill phagocytes, increase capillary cell permeability and damage the clotting mechanism. Capillary thrombosis occurs and there is leakage of fluid through the damaged capillary epithelium. Blood pressure falls and the animal lapses into shock. The toxic complex also blocks the opsonizing activity of the C'3 factor of complement and so phagocytosis is reduced. The net effect of the toxic complex on the animal is to produce edema, shock, and death. These effects can be neutralized by specific antiserum. A lethal quantity of toxin is elaborated some time before the organism attains the populations found when the animal dies. Thus antibiotic therapy must be initiated early in the course of the infection before a lethal concentration of toxin has been elaborated.
Table 1. Components of toxic complex of B. anthraces ________________________________________________________
Component Chemical nature
________________________________________________________
I (Edema factor) Protein carbohydrate
(chelator)
II (Protective antigen) Protein M.W. 100,000
III (Lethal factor) Protein
_________________________________________________________
Table 2. Toxic components of B. anthraces needed for lethality, edema, and immunogenicity __________________________________________________________ Components needed for
__________________________________________________________ Lethality Edema Immunogenicity
__________________________________________________________
I + II I + II I + II
II + III I + II + III II + III
I + II + III I + II + III__________________________________________________________Anthrax usually assumes a localized form in swine, sheep and horses. These animals are infected only by eating heavily contaminated feed, either the raw meat of animals which have died of anthrax, or in the case of swine, infected bone or meat meal given as a feed supplement.
Generalized anthrax may easily be induced in susceptible animals by the inhalation of spores. Infection in man of this type occurs among employees of plants in which hides, wood and hair are processed, the spores being thrown into the air from the infected material when handled. The human form of anthrax known as "Woolsorter's Disease" is a rapidly fatal malady.
26.3.1.2.9 Postmortem Lesions:
Rapid petrification of the carcass is a characteristic of anthrax. The blood is very dark and tanny, and rigor mortis is never complete. Gas forms in the intestine, and they are generally distended. The mucosa is cyanotic, and blood exudes from the body. The spleen usually shown enlargement, particularly in the horse. In swine, the disease is manifested by an acute pharyngitis with extensive swelling and hemorrhage of the throat region. In the dog and cat, the disease is similar to swine, but also shows a very severe gastroenteritis
26.3.1.2.10 Laboratory Diagnosis
Identification of the disease by means of recognition of the organism or its products may be made in a number of ways. Probably the most important are:
- 1. Microscopic, direct smear.
- 2. Guinea pig and mouse inoculations for isolation of the organism. Mouse gives quicker results (24 hours) while guinea pig takes 48 hours.
- 3. Ascoli test (not routinely used in USA).
- 4. Cultural methods--when the tissues are fresh, there is no difficulty in cultivating the causative organism.
26.3.1.2.11 Prognosis
- 1. Unfavorable in peracute cases.
- 2. Cases with early elevation of temperature respond to immune serum and penicillin.
- 3. Some cases recover without treatment.
26.3.1.2.12 Treatment
Penicillin has a marked therapeutic value in curing anthrax. Not less than 1 million units daily until recovery should be given. Sulfonamides (sulfamerazine and sulfathiazole) at the rate of 1 grain/lb/day have also been used. Aureomycin and terramycin are also effective. Immune serum has been shown to be of value.
26.3.1.2.13 Biologics
Immunization is of definite value. Antibody which is produced precipitates capsular substance and makes phagocytosis of organisms possible. The three basic reasons for use of immunizing agents are: preseasonal immunization; in case of an outbreak; and treatment of cases.
The immunizing products used are:
1. Pasteur vaccine is the basis of all vaccines.
- a. No. 1--Organism attenuated by growing at 42-430C for 24 days will kill mice but not guinea pigs or rabbits. A permanent attenuated organism was not enhanced by subsequent culture at 370C.
- b. No. 2--Organism grown for 12 days at 42-430C so as to kill mice and guinea pigs but not rabbits. Pasteur vaccine has been used extensively but has been objected to because it produces anthrax in highly susceptible animals and requires two handlings. In addition, some products become non-viable due to autolysis of organisms.
2. Anthrax Spore Vaccine: Variations of attenuation are made by different manufacturers. Some companies label them No. 3 and No. 4. Some are made in between No. 1 and No. 2, particularly the vaccine given the second time to sheep and goats. (No. 1 kills mice; No. 2 kills mice and guinea pigs; No. 3 kills mice, guinea pigs and occasionally rabbits, No. 4 kills rabbits). The Stern strain of organism, an attenuated strain developed in South America, does the same as the Pasteur vaccine.
3. Intradermal Anthrax Vaccine: Usually conforms to Pasteur No. 2 in potency.
4. Saponified vaccine "Carbo-zoo": This is essentially Pasteur No. 2 vaccine suspended in 10% saponin (glucoside, C32H54O18) which is employed as an irritant to enhance immunity.
5. Anthrax bacteria: Composed of a suspension of B. anthraces young culture killed usually with formalin. It is tested by culturing and animal inoculation to determine safety.
6. Anthrax Serum: Preparation--Basic immunity in horses and cattle followed in 10 days with virulent culture. The dosage is increased until potent antiserum is obtained. Tested in rabbits--2 cc serum protects rabbits against 104 fatal doses of culture.
Used as a curative; prophylactic with spores. Used alone in areas prohibiting spore vaccine.
26.3.1.2.14 Control
Regulations
1. State
- a. Most states list anthrax as a reportable disease.
- b. Requires quarantine on premises.
- c. Regulates us of immunizing agents.
- d. Requires disinfection of transporting cars and trucks.
2. Federal
- a. Concerned with interstate commerce.
- b. Requires disinfection of transporting cars and trucks.
- c. Meat inspection regulation is important.
26.3.1.2.15Sanitation in Anthrax
1. Total Destruction of carcass and bloody exudate:
- a. Rendering plant.
- b. Burying 6 feet under with lime.
- c. Burning must be complete.
- d. Treatment of infected pasture.
2. Disinfection of contaminated surfaces:
5% aerosol, 1:1000 HgCl2, 5% lye
26.3.2.1 General Description
The Corynebacteria are a ubiquitous group of Gram-positive, rod-shaped bacteria that are not acid-fast, do not form spores, and with few exceptions, are nonmotile. Gram-positive rod like forms are usually arranged in a palisade. The organism will grow aerobically or under microaerophilic conditions, but is often capable of anaerobic cultivation. The characteristic morphology in stained smears is groups of cells arranged in a palisade and individual cells lying at smears is groups of cells arranged in a palisade and individual cells lying at sharp angles to one another in L and V formations. Club-shaped swelling from growth on Loeffler's coagulated sera medium or Pai's coagulated egg medium. Pleomorphism is common.
Those species which attack carbohydrates produce acid but not gas. With two exceptions (C. haemolyticum and C. pyogenes), the Corynebacteria are catalase positive. Those species commonly recognized as pathogenic for man and animals do not produce indole, but nitrate reduction, gelatin liquefaction and urea hydrolysis are variable.
Corynebacteria are numerous on the surfaces of mucus membranes. Most are part of the normal flora, are not well defined, and are often commonly referred to as "diptheroids", a term used to denote the harmless saprophyte rather than one of the recognized pathogens. Important Corynebacterium pathogens for domestic animals are those such as C. equi, C. ovis, C. pyogenes and C. renale. These are rarely encountered in human infection. In addition to C. diphtheria, C. haemolyticum and C. ulceran are pathogenic for humans.
Corynebacterium equi: Purulent Pneumonia in Foals.
26.3.2.2 Etiology:
Corynebacterium equi causes a purulent pneumonia in foals and is often found in tuberculosis-like lesions on the cervical lymph nodes of swine.
26.3.2.3 History:
The organism was described and named by Magnusson in southern Sweden in 1923 as the causative agent of purulent pneumonia in foals which frequently was associated with pyemia. Holth and Amunden in 1936 described tuberculosis-like lesions in the cervical lymph nodes of swine which they attributed to coccobacillus. Dimock and Edward and other found C. equi in this country in foals.
26.3.2.4 Morphology and Staining Reactions:
Corynebacterium equi is a rather large organism that shows considerable pleomorphism, ranging from coccoid to bacillary forms. In fluid media the organism is usually bacillary; on solid media the form is usually coccoid. Metachromatic granules can usually be demonstrated, especially in cultures grown in milk. This organism is Gram-positive and especially in cultures grown in milk. This organism is Gram-positive and stains readily with other dyes. Some workers claim that acid-fast forms are demonstrated in old culture, but others have been unable to confirm this.
26.3.2.5 Cultural Features:
Colonies are pink and moist, especially old cultures that are grown on potato. Good growth occurs on all the ordinary media. There is a rather poor growth in milk, without coagulation or other evidence of change in the chemical composition. The organism is nonmotile, catalase positive, gelatin negative, and urea is often positive but may be delayed. Glucose, maltose and sucrose are not fermented. The organism may be isolated from the blood, urine, cerebrospinal fluid, sputum and water.
26.3.2.6 Resistance:
The organism does not appear to be especially resistant to ordinary physical and chemical agents, but does have a surprising resistance to acids. Corynebacterium equi is resistant to the action of 2.5% oxalic acid for 1 hour, and this unique property enables one to isolate the organism from tissues contaminated with other bacteria.
26.3.2.7 Mode of Transmission:
Little information is available on the mode of transmission of this organism. Some workers expressed the belief that it lives in the soil, but no proof has been provided that this is the case.
26.3.2.8 Symptoms and Clinical Features:
The infection sometimes arises in foals when they are about 2 to 4 months old. Usually the affected foal has suffered no previous illness. The onset of the disease is characterized by dullness, increased temperature, rapid pulse and respiration. A cough develops, the eyes water, and there is a purulent nasal discharge. Moist rales develop in the lungs. The foal becomes weak and emaciated and dies. The course of the disease is 6 to 14 days, and the mortality is high.
26.3.2.9 Diagnosis:
In the foal, the disease can be distinguished from strangles because, in a C. equi infection, lesions are not found in the lymph nodes of the head. As a rule, it occurs later in the life of the foal than does navel or joint ill. A definite diagnosis usually depends on the isolation of the causative agent.
26.3.2.10 Immunity:
No practical methods of immunization against C. equi have been developed. Several serological types in this species can be demonstrated by agglutination tests.
26.3.2.11 Pathogenicity in Horses:
In one study, C. equi was found in 23 of a series of 78 cases of suppurative pneumonia in young foals. The thoracic lymph nodes were greatly enlarged and suppurative in these cases. In none of these cases were any lesions found in the lymph nodes of the head, a feature by which this disease can be differentiated from strangles. Abscesses in the liver, kidney and spleen are rarely found. The disease has been seen in Kentucky and California. The organism has been isolated from the uterine discharge of a number of aborting mares in Kentucky and is suspected of being the causative agent.
26.3.2.12Pathogenicity in Swine:
The infection in swine occurs in the cervical lymph nodes. It is doubtful whether the organism is of much economic importance here.
26.3.2.13 Chemotherapy:
The infection is not mitigated by presently known chemotherapeutic agents. Prevention appears to be influenced by good hygienic practices in caring for the mare and foal.
26.3.2.14 Control Measures:
There are no known methods of preventing infections with C. equi except general sanitary measures, which may minimize but will not eliminate them.
26.3.2.15 Public Health:
So far as is known, C. equi is not pathogenic for man.
The Preisz-Nocard bacillus, Corynebacterium ovis
An infection by C. pseudotuberculosis (ovis) occurs in sheep, horses, cattle, goats, deer and rabbits. The organism has been isolated from the lymph nodes and appendix of man. Caseous lymphadenitis occurs in sheep rather generally in the western United States and Canada and is reported also from Argentina, Uruguay, Chile, Australia and New Zealand.
The organism is a pleomorphic rod. Frequently it is so short that it may easily be mistaken for a coccus. In the caseous pus from lymph nodes, it sometimes occurs as rod forms that resemble very closely the human diphtheria. It does not form spores, and is nonmotile. It retains the Gram stain but is not acid fast.
The organism will grow on all the ordinary media, although not luxuriantly. Colonies on agar are quite characteristic; they grow slowly and do not reach maximum size for several days when incubated at optimum temperature (370C). The color is grayish to yellowish, and the surface is dull and dry. They fragment easily when touched with a needle. When fully developed, they have papilliform centers surrounded by concentric rings that parallel the irregular margin.
On blood agar the colonies are slightly hemolytic. The organism grows well on Loeffler's blood serum but does not liquefy it. Growth occurs in milk but there is little change in the appearance on the medium. On broth a fragile pellicle is formed. Glucose and maltose are fermented without gas formation. Lactose, sucrose, raffinose, dextrin and inulin are not attacked. The organism produces a soluble toxin in the various culture media that is similar to, but not so potent as, that of the human diphtheria bacillus. It is claimed that this toxin was partially neutralized by diphtheria antitoxin, but the relationship between the
soluble toxin and that of the diphtheria has not been confirmed.
SHEEP: Caseous lymphadenitis is a chronic disease in which clinical signs and lesions may not be observed until several months after infection. The disease affects the lymph nodes, especially those of the chest. Eventually the infected glands become converted into large encapsulated abscesses. In generalized cases, the lesions may be distributed throughout the lungs, liver, kidney and spleen, and the corresponding lymph nodes. In the younger lesion the pus is butyrous; in lesions of long standing the pus becomes rather dry and granular, and firm masses are usually arranged in concentric layers within a thick fibrous capsule.
Sheep between 2 and 4 years of age contain the highest percentage of infected animals. Twenty percent of all animals found infected with caseous lymphadenitis on post mortem inspection are condemned. Corynebacterium pseudotuberculosis is believed to enter the body largely through skin abrasions, principally at the time of shearing. A few animals are infected through the unhealed navel and through docking and castration.
CATTLE: There have been a few reports of the infection. It has been found in a case of bronchopneumonia in a cow and also in calves and the so-called "skin lesion" of tuberculosis of cattle in Utah and California. In areas where skin lesions are commonly found, C. pseudotuberculosis has been isolated from some of the lesions taken at biopsy or at post mortem examination of the lesion-free tuberculin reactor animals.
HORSES: Ulcerated lymphangitis resembles the cutaneous form of glanders in horses. It is characterized by nodules, ulcers and inflammation of the lymph vessels, especially in the region of the fetlock, but occasionally extending up the legs. The nodules appearing on the leg usually break down to form ulcers, which exude a thick greenish pus usually mixed with blood. The onset is very slow and usually manifests itself by pain and swelling of both legs. The marked involvement of the lymph nodes, so characteristic of the disease in sheep, is not seen in the horse. Infection by inhalation of contaminated dust may also occur, the primary lesions then developing in the lungs.
Chronic single or multiple abscesses, known as "false distemper" or "Wyoming strangles", is another manifestation in horses. The pathogenesis and transmission are unknown. However, distribution corresponds to that of sheep in western states. The highest incidence is in late summer and early fall.
Generally, the manner in which infections with organisms are spread is not known. It is suspected to be related to soil contaminations. The location in the fetlock region of the horse suggests this. Most infections are probably encountered through skin abrasions. In sheep, infection may occur through docking, castration and shearing wounds, though this is largely speculation. Dust inhalation in sheep is probably a mode of transmission.
The diagnosis of caseous lymphadenitis in sheep can be made by careful palpation of all external lymph nodes or, in the case of internal infection only, by the appearance of the characteristic lesions at necropsy. Serologic tests alone are not diagnostic. However, the com
