Current Progressive Dairy digital edition
Advertisement

0507 PD: Detecting and treating salmonellosis

R.M. Thornsberry Published on 09 May 2007

Salmonellosis is a disease of all animals caused by the genus Salmonellae and usually characterized by one or more of three major syndromes:

1) Septicemia (a blood infection)

advertisement

advertisement

2) Acute enteritis (infection and inflammation of the intestinal tract)

3) Chronic enteritis (a long-term infection and inflammation of the intestinal tract)

The disease occurs in every location around the world, and the incidence of the disease increases with the intensification of livestock husbandry.

Salmonellosis is an oral-fecal contact disease. The microorganisms that cause salmonellosis are shed in the feces. Animals come in contact with feces when they drink contaminated water, contaminated feed or simply come in contact with fecal matter. Salmonellosis has a somewhat increased incidence in poultry and birds, some rodents, and many reptiles. Salmonellosis is a zoonotic disease, spreading from animals to man.

Once human patients become infected, some patients may develop into chronic carriers and spread the disease. Livestock owners and livestock husbandmen should be very careful while handling and treating animals known to be infected with salmonellosis. The disease in humans can be deadly.

advertisement

There are many species of salmonellosis. Good diagnostic skills are required to identify which species is causing disease in a specific group of animals, reptiles, poultry or humans. It is generally believed all poultry and eggs are potentially contaminated with salmonellosis.

Salmonellosis organisms may survive for months in a wet environment. Rodents and birds are common carriers of salmonellosis and are regular sources of contamination of both feed and water. Animals in stressful situations; animals with concurrent, unrelated diseases; or animals that have received prolonged hospitalization treatment are at an increased propensity to develop salmonellosis.

Salmonellosis tends to be a disease of the young and old, but it is not limited to those two age groups.

While younger animals do not readily become chronic carriers, a chronic carrier status is common in older or adult animals that develop salmonellosis. These carrier animals become a source of infection to animals kept in close association or animals grazing with the carriers. Chronic carriers may revert to acute cases at any time, usually following a period of stress, transport or development of concurrent, unrelated disease.

In cattle, salmonellosis usually becomes endemic (reoccurring regularly) on a given farm facility. Outbreaks are often explosive, particularly following a period of weather stress, introduction into a new or different environment or presence of a concurrent, unrelated disease such as cryptosporidiosis. Animals that develop salmonellosis usually develop a diarrhea, with or without blood, depending on the species and the pathogenicity of the salmonellosis organism.

Infected animals quickly become depressed, have an elevated body temperature and lose their appetite. If not treated, animals will die within 24 to 48 hours. Death is usually caused by the salmonellosis organisms gaining access to the blood stream. Once in the blood stream, the bacteria invades key tissues, grows rapidly, secretes endotoxins and eventually causes shock, followed by cardiovascular collapse and death.

advertisement

In cattle, concurrent infection with E. coli, cryptosporidiosis, BVD, rio virus, corona virus, and clostridium perfringens causes the severity of symptoms of salmonellosis to be exacerbated. Animals receiving antibiotics are thought to have the microflora altered, setting up a noncompetitive environment that promotes the growth of salmonellosis bacteria. A specific antibiotic sensitivity test is required to determine the proper antibiotic to utilize in treating salmonellosis.

Systemic antibiotics (injectable) are required to treat septicemia that commonly develops with salmonellosis. Consult your local veterinarian for his or her suggestions as to treatment options while a specific antibiotic sensitivity test is being performed. Concurrent fluid therapy to treat dehydration due to enteritis and electrolyte therapy to treat acid-base imbalances are common supportive treatment options.

In acute outbreaks, there is the option of utilization of salmonellosis antiserums. An antiserum is a blood product taken from animals repeatedly vaccinated against salmonellosis. Antibodies against salmonellosis are concentrated in the antiserum and utilized as an injection to neutralize both salmonellosis toxins and the infective bacteria.

Calves with salmonellosis will usually have small hemorrhages throughout the body, especially on the surfaces of organs, the surfaces of the intestines and on the surfaces of the lungs and heart when an autopsy examination is performed. Calves will exhibit scours that will be pasty to watery, yellow to brown, to bloody. The feces will have a dead odor because of the severe damage done to the lining of the intestines and the resulting death of tissues. Often, the entire lining of the intestine will slough off and, when passed in the feces, will take on the appearance of a piece of intestine to the untrained eye. These sloughed tissues are called intestinal casts.

Salmonellosis can be prevented. Remember, cleanliness is next to Godliness. Keep the environment free of wild birds, domestic poultry, rodents and fecal matter buildup. Keep the environment dry, well bedded and clean.

There are commercial bacterins and toxoids to utilize in immunization programs against salmonellosis, but the best results are obtained from autogenous bacterins. Autogenous bacterins are produced by special laboratories utilizing the exact salmonellosis bacteria causing disease on the problem farm or production facility. Your local veterinarian is the best source for development and utilization of an autogenous bacterin. Salmonellosis organisms are relatively poor antigens. This means repeated vaccination is required to develop any level of immunity.

It does not do much good to vaccinate calves younger than 4 weeks old. These young calves do not have a fully developed immune system and do not routinely respond well to vaccination against salmonellosis. Repeated vaccination of dry cows, at freshening, at dry-off and again three weeks prior to calving may develop enough antibody production to pass some of the antibodies into the colostrum. Feeding at least 4 total quarts of high-quality colostrum before the calf is 12 hours old may be of possible assistance in dealing with salmonellosis on a given infected farm or production facility. Prevention is very important in dealing with salmonellosis because once newborn calves become infected with the salmonellosis bacteria, individual treatment is usually unsuccessful.

A relatively new approach to dealing with a bacterial disease like salmonellosis has been presented in the scientific literature and many clinical veterinary publications – the use of nutraceuticals to aid in the prevention of bacterial diseases in baby calves.

Although there are any number of nutraceuticals that have been evaluated, the use of oligosaccharides and mannan oligosaccharides (MOS) in particular, has become an acceptable practice. MOS can be added to milk, milk replacers and starter feeds. They are fed continuously during the time of possible exposure to pathogenic bacteria.

While it is beyond the scope of this article to identify all the modes of action of MOS, it basically acts as a point of attachment for pathogenic bacteria. Cells lining the intestinal tract of animals have a mannan-like point of attachment for pathologic bacteria. MOS are a mannan derivative that tricks the bacteria into attaching to it rather than the intestinal cells. The bacteria are then carried out of the body in the bowel movements, preventing the pathological bacteria from causing disease or entering the blood stream.

Acceptance of the use of a neutraceutical such as MOS has become almost universal in U.S. dairies. Evaluation of the use of this neutraceutical in other species besides baby calves is ongoing. PD

References omitted but are available upon request at

LATEST BLOG

LATEST NEWS