Is there a Link between Mastitis and Endotoxins in High Producing Dairy Cows?
Bovine mastitis is the most costly infectious disease in dairy cattle, buffalo, sheep and goats. Gram-negative bacteria are responsible for many clinical conditions observed in cattle. Coliform mastitis is a common disease initiated by gram-negative opportunists, and can devastate dairy production. This develops in the first 100 days of lactation encompassing all degree of severity.
Gram-negative bacteria are found in the environment of the dairy animal and thus, are designated as environmental mastitis pathogens. This class of bacteria occupy many habitats in the cow’s environment. Escherichia coli are normal inhabitants of the gastrointestinal tract of warm blooded animals. Both Klebsiella spp. and Enterobacter spp. can be found in soils, grains, water, and intestinal tracts of animals. Serratia marcesens are also found in many of the same environmental sources as Klebsiella spp. and Enterobacter spp. Pseudomonas spp. and Proteus spp. commonly contaminate water hoses used to wash udders in the milking parlor before milking.
Coliform bacteria can be isolated from any surface area of the cow and cause a host of diseases other than mastitis. These bacteria commonly cause mastitis, respiratory disease and reproductive diseases in dairy cows. Intramammary infections caused by coliform bacteria typically result from entry of the bacteria via the teat canal and multiplying in the gland.
Coliform mastitis = “Mediator Shock”
Coliform mastitis results in the release of a cascade of inflammatory mediators such as:
- Complement Cascade
- Tumor Necrosis Factor
- Colony-Stimulating Factors
- Procoagulent Activity
- Platelet Activating Factor
Bovine mammary glands are an excellent model for study of coliform mastitis because induction of inflammation, collection and isolation of inflammatory cells is easily accomplished. Each mammary gland serves as a separate experimental unit. The pattern of gram-negative bacterial growth is predictable in that bacterial counts in the gland will increase rapidly after inoculation.
After the live-organism challenge, milk production typically will drop from 7 kilograms (60 lbs.) to approximately 2.0 kilograms per milking by 12 hours after inoculation and will continue to decline to less than 1.0 kilogram per milking by 60 hours after inoculation. Milk production remains low for approximately 180 hours and then may begin a gradual increase. Over a period of days to weeks, milk production may attain approximately a third of its original amount and may return to pre-inoculation values in several weeks to months.
Somatic cell counts
Somatic cell counts should be less than or equal to 105 cells/ml after inoculation it will increase to 106 cells/ml by 12 hours after inoculation with higher counts over 24 hours. This adversely affects milk quality and potentially food safety issues due to therapeutic antibiotic use.
Coliform Mastitis and its effects on reproduction
Reproductive failure is one of the leading causes of economic loss in the modern dairy. Bacterial multiplication and endotoxin liberation associated with clinical gram-negative bacterial mastitis will cause the release of inflammatory mediators with subsequent luteolysis if the CL is in its fifth to seventeenth day of development. If the fetus is in the first trimester of development, it is common for coliform mastitis to cause abortion. When coliform mastitis occurs during the third trimester of fetal development, it may cause early calving which results in a weak and poor-doing calf.
Current treatment and management practices are only moderately successful. Gram-negative organisms are responsible for many diseases of ruminants, including neonatal coliform septicemia, coliform mastitis, salmonellosis, pneumonias caused by Pasteurella spp. and Actinobacillus spp., brucellosis, metritis, campylobacteriosis, infections of the cornea and sclera and thromboembolic meningoencephalitis. Most of the clinical infections and mortality resulted from gram-negative organisms, specifically Escherichia coli and Salmonella spp. mortality varied among farms and production; however, estimates of dairy calf death losses during the first 8 weeks of life range from 2.5% to 29% Septicemia caused by E. coli generally affects calves less than 1 week old and is characterized by a rapidly fatal course. Death losses from salmonellosis in cattle are most severe in confinement-raised dairy calves at 1 to 10 weeks of age. Salmonellosis is usually confined to the gastrointestinal tract, whereas most calves develop bacteremia with spread of the infection to liver, lungs, bone marrow and CNS.
Clinical signs associated with Gram-Negative Bacterial Diseases in Ruminants
Morbidity and mortality associate with gram-negative bacterial sepsis appear to be consequences of host reaction to bacterial cell wall components such as endotoxin, the lipopolysaccharide cell wall component of gram-negative bacteria. The general effect of endotoxins are well chronicled and are reported to include lethargy, respiratory distress, transitory hyperthermia followed by hypothermia, decreased systemic blood pressure, increased heart rate followed by decreased cardiac output, diarrhea, changes in blood cell counts, and alterations in the blood coagulation system.
Respiratory tract infections in calves
Bovine pneumonic pasteurellosis (BPP) is a common respiratory disease in many age groups. Although the precise mechanism inducing the BPP in not understood, other microbial agents and stress predispose cattle to respiratory tract disease. In this study BHV-1 infection alone induced clinical respiratory tract disease that was exacerbated by P hemolytica.
Coliform mastitis is common in both small-holder farms and larger dairy farm operations. The incidence can range from 1% up to 40% of the clinical mastitis cases. The subclinical incidence may be even higher. As the management of the farm controls Gram-positive contagious mastitis pathogens, e.g. Staphylococcus aureus, the somatic cell count goes down, but the risk of coliform mastitis increases. Therefore, management must seek out additional methods of controlling inflammatory events such as mastitis, respiratory disease and rumen inflammatory events that may cause endotoxin release into the circulatory system.
- There are over 3,500 different serotypes of coliform bacteria.
- At any one time, there may be at least 15 different serotypes on a dairy farm, and these can vary from farm to farm and year to year.
- A common solution to reduce the incidence and severity of coliform mastitis is excellent hygiene and vaccination with the J5 E. coli CommonCcore Antigen Vaccine.