Streptococcus spp bacteria are a common commensal bacteria of mucous membranes of cats.
Important clinical pathogens in cats include:
- Streptococcus canis
- Streptococcus equi sub zooepidemicus
- Streptococcus suis
Most Streptococci are non-pathogenic, but a few species can cause significant morbidity and mortality ranging from death in young kittens, to pyometra and respiratory disease such as pneumonia. Streptococcus canis, a particularly pathogenic bacteria in cats, utilise novel receptors for a proteolytic plasmin protein (mini-plasminogen) to induce fibrinolytic activity on mucous membranes and transmigration into the blood.
Beta(β)-haemolytic streptococci (e.g. Streptococcus canis) has been incriminated as causing mortality in kittens, usually in the first few weeks of life. S. equi sub zooepidemicus has also been reported as fatal in adult cats following infection transferred from dogs. The environment and Queens are suspected as sources of kitten infections (e.g. vaginal discharge, milk, faeces, oropharynx, skin).
These bacteria are a common pathogen in catteries and shelters. Beta-haemolytic streptococci belong to the Lancefield groups A, B, C or G classification.
Many factors can predispose kittens to neonatal septicaemia: failure of passive transfer of antibodies (inadequate colostrum intake, or inadequate antibody levels in the queen), high levels of pathogenic bacteria in the birth canal or from the queen (saliva, milk), unhygienic environment, failure of passive local immunity (inadequate nursing, or inadequate immunoglobulin levels in milk). Pathogenic bacteria may enter the kitten via the mouth, intestinal tract, genital or urinary tract, or umbilical cord. The most important routes of infection are the mouth and the umbilical cord. Kittens may show signs of difficulty breathing associated with blood loss (usually chest cavity) and secondary pneumonia, but sudden deaths are also common.
S. canis is found in the vaginas of about 50% of young queens. The carriage rate in queens up to 2 years may be 100% in some catteries. Generally, the queens themselves are healthy. The highest incidence of infection is in kittens from the first litter born to a young queen (under 2 years). Older queens are more likely to have eliminated the bacteria spontaneously. Toms can also carry the bacteria in their prepuce, leading to rapid spread of the bacteria in a naive cattery.
Omphalophlebitis (umbilical infection) results when pathogenic bacteria from the queen's saliva or the environment invade the umbilical cord. Normally, the queen chews off the umbilical cord a few inches from the body wall. The cord quickly dries which limits bacterial invasion of both the cord and the umbilicus. If the cord is severed too short, especially if it is severed flush with the abdomen, bacterial invasion may occur or an umbilical hernia may result. An abscess may form at the umbilicus, either just under the skin, or inside the abdomen. Bacteria may also enter the bloodstream via the umbilical vein (which stays partly open for several days) and cause septicaemia. The two most common agents of omphalophlebitis are haemolytic E. coli and Streptococcus canis. If the cause of the infection is not immediately known, antibiotics with coverage of both gram-negative and gram-positive organisms should be chosen (e.g. enrofloxacin and cephalexin once daily if under 2 weeks of age).
Streptococcus canis was first identified as a cause of neonatal mortality in the mid-1980s. Most affected kittens die between 5 and 10 days. They may have no clinical symptoms of illness until hours before death, although they often gain weight slower than their uninfected littermates. Some may have focal abscesses in the umbilicus, testes, or lungs as evidence of routes of bacterial entry into the body. Skin ulceration and chronic respiratory infection that progressed, in some kittens to necrotizing sinusitis and meningitis.
A transient fever may be present in the 24 hours prior to death. Kittens are infected with the bacteria from the queen's vagina during birth. Usually not all of the kittens in the litter are affected. An abscess of the umbilicus spreads into the liver and abdominal cavity, leading to peritonitis and septicaemia. Some kittens may have an obvious umbilical abscess or swelling. The diagnosis is confirmed by culture of the umbilicus, liver, peritoneal cavity or lungs at necropsy.
A second syndrome associated with S. canis is also seen where kittens develop abscessation of lymph nodes in the neck at about 3 - 6 months of age.
In adult cats, Streptococci have been incriminated in cases of otitis media/otitis interna and subsequent meningoencephalitis, including Streptococcus equi sub. zooepidemicus. Myocarditis and necrotising fasciitis and myositis with pneumonia and septicaemia has been reported in cats due to S. canis. Pneumonia, pleuritis, focal encephalitis, myocarditis and nephritis have also been observed in adult cats.
Antibiotic therapy is rarely effective in eliminating S. canis from a queen's vagina. However, a single dose of combined procaine and benzathine penicillin given to the queen at parturition may temporarily suppress the S. canis population and decrease risk of infection in the kittens.
Kitten mortality from S. canis is the highest when the bacteria first enters a cattery. Thereafter, any naive queens entering the cattery may become infected and have a high mortality rate in their first litters. Most affected kittens die too quickly for effective treatment. Since S. canis is almost uniformly sensitive to penicillin, remaining littermates can be treated prophylactically with oral amoxicillin paediatric suspension (every 12 hours for 5 days).
The risk of kitten mortality from S. canis can be managed prophylactically in catteries. The umbilical cord should be dipped in 2% tincture of iodine promptly after birth. In catteries experiencing recent kitten deaths from S. canis, kittens can be given a single SC injection of 0.25 ml of a 1:6 dilution in sterile 0.9% saline of product containing 150,000 IU/ml benzathine and procaine penicillin G.
Queens are best treated with prophylactic doses of amoxicillin/clavulanate and/or azithromycin for 2-3 weeks prepartum. Other antibiotics such as enrofloxacin, marbofloxacin and pradofloxacin have been reported as effective in some cases.
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- Dr Jim Euclid pers comm
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