EVOLUTION

ANIMAL BREEDS

DISEASES

MEDICATIONS

FOOD/FEED

BEHAVIOUR

EXOTIC ANIMALS

SPECIAL SECTION

Bacterial Disease - Leptospirosis

Synonym: Cattle (Redwater of calves)

Etiology:

In the USA, the disease is primarily due to the Leptospira serovars hardjo, L.pomona, L.grippotyphosa. However L.canicola and L.icterohaemorrhagiae serovars also have been isolated.

Clinical findings

Calves may have ever, anorexia and dyspnea, and in Leptospira Pomona infections, icterus, hemoglobinuria, and anemia.

Body temperature may rise suddenly to 105-106 F(40.5-41°C). Haemoglobinuria rarely lasts longer than 48-72 hour.

Icterus clears rapidly and is followed by anemia.

The RBC begins to increase in number by 4-5 days and return to normal 7-10 days later.

However, L.hardjo infections usually do not cause hemolytic anemia, which makes diagnosis more difficult. Morbidity and mortality are higher in calves than in adult cattle.

Lesions

In the acute form, anemia, icterus, hemoglobinuria and submucosal hemorrhages are prominent. The kidneys are swollen, with multifocal petechial and ecchymotic hemorrhages that become pale with time.

The liver may be swollen, with minute areas of focal necrosis. Petechiae in other organs are seen in fulminating cases; however, in the more prevalent L.hardjo infections the lesions are primarily restricted to the kidneys.

Diagnosis

Serology with paired serum samples, direct culture in special media, or fluorescent antibody techniques on tissues are used to confirm clinical and postmortem findings.

In herd evaluation, sera should be obtained from various age groups. MAT titers may peak before abortion because the acute infection occurred several weeks previously.

Abortion due to L.hardjo infections may occur with low or negative serologic titers.

Treatment

Chlortetracycline and oxytetracycline have been reported to be successful if given early.

Blood transfusions may be indicated if the anemia approaches the critical level. Treatment has limited effect on the course of disease once uremia has developed.

Management of infected herds merits special consideration. When leptospirosis is diagnosed in pregnant beef cows during the early epizootic phase, further abortions can be prevented by prompt vaccination of the entire herd and simultaneous treatment of all animals with appropriate antibiotics.

The antibiotic reduces the number of leptospires in the kidneys and other tissues, at least during treatment, and provides a measure of protection until immunity is induced by vaccination.

In dairy herds, generally only the sick animals should be treated with antibiotics because the loss of market milk after treatment must be considered.

Prevention

Annual vaccinations, confinement rearing, and chemoprophylaxis are used for control.

Bacterins generally confer protection against abortions and death and significantly reduce transmission include rat control, fencing cattle from potentially of replacement stock from herds that are seronegative for leptospirosis, and chemoprophylaxis and vaccination of replacement stock.

Leptospirosis in Dogs

The most common Leptospira serovars infecting dogs were reported to be L.canicola and L.icterohamorrhagiae in older studies, but Pomona and grippotyphosa have been the most common isolates in recent studies.

This shift may represent exposure of pet dogs to infected wildlife such as raccoons and opossums, which inhabit suburban and urban areas.

Clinical findings

Dogs of all ages may be affected, and there is no sex predilection. He incubation period is 4-12 days.

Nonspecific signs such as fever, depression, anorexia, and generalized pain may be seen during this time.

Vasculitis, thrombocytopenia, and coagulopathy may develop.

Within a few days, additional signs of uremia, such as dehydration, vomiting, and oral ulceration, are seen.

The liver is variably affected, and the degree of icterus often reflects the severity of the disease. Meningitis, uveitis and abortion have been rarely reported.

Hematologic abnormalities include leukocytosis, lymphopenia, monocytosis and thrombocytopenia.

Serum chemistry may reveal azotemia and electrolyte disturbances secondary to the renal failure, including hypoatremia, hypochloremia and hyperphosphatemia. Serum levels of hepatic enzyme (AST, ALT, alkaline phosphatase) and serum bilirubin increase if the liver is affected. Urine sediment usually contains RBC, WBC and granular casts. Isosthenuria, proteinuria, and glucosuria reflect tubular damage.

Lesions

In acute disease, the kidneys or liver, or both are swollen.

Hemorrhages may be present in any organ.

Other lesion may include any of those seen with acute uremia.

In chronic cases, white or gray foci or streaks may be seen in the kidney and liver.

Histologically, lesions in acute disease are those of acute uremia, including acute interstitial nephritis and possibly hepatitis.

In chronic disease, the only lesions may be chronic interstitial nephritis or chronic active hepatitis, or both.

Diagnosis

Diagnosis is based on demonstration of leptospires in urine or tissues and serology, in conjunction with typical clinical and laboratory abnormalities.

Treatment

Renal failure and liver disease are treated with fluid therapy and other supportive measures to maintain normal fluid, electrolyte, and acid-base balance.

Antibiotic therapy consists of penicillin, tetracycline, or doxycycline to eliminate leptospiremia, followed by tetracycline or doxycycline to eliminate the renal carrier phase.

Tetracycline should be used with caution in azotemic animals. The fluoroquinolone antibiotics such as enrofloxacin also appear to be leptospirocidal.

Prevention:

Commercial bacterins for dogs consist of the inactivated serovars canicola and icterohaemorrhagiae.

There does not appear to be good cross-immunity between serovars, and vaccinated dogs may still be susceptible to infections with other serovars. Vaccination is recommended at yearly intervals but may be needed more frequently in enzootic areas.

Dogs that have recently been exposed to leptospirosis are treated prophylactically with penicillin or doxycycline for 7-10 days to prevent infection.

Leptospirosis in Horses

Leptospirosis in horses is most commonly associated with uveitis or abortions.

Systemic disease as described for cattle can occur but is rare.

During investigations of the etiology of equine uveitis, serology revealed that many affected horses and high titers to Leptospira Pomona, and the organism has been isolated from eyes of horses. It is not clear whether the uveitis is due to intraocular infection or is immune mediated.

Leptospirosis has recently been incriminated as the cause of a significant number of equine abortions; in the USA, the serovars grippotyphosa and Pomona type Kennewick have been isolated from aborted equine fetuses.

Measures for control and treatement are similar to cattle and pigs, but specific bacterins have not been developed for horses.

Uveitis is treated symptomatically to reduce inflammation and prevent synechiae.

Leptospirosis in Pigs

Although Pomona was the serovar most commonly found in pigs, recent serologic, surveys indicate brastisalava is the most widespread.

Infection usually is from contact with the urine of other pigs or wildlife.

Other Leptospira serovars reported in pigs include grippotyphosa, canicola, tarassom, muenchen, and icterohaemorrhagiae.

Abortions occurring 2-4 weeks before term are the most common manifestation of leptospirosis in pigs.

Piglets produced at term may be dead or weak and may die soon after birth.

Differential diagnosis

SMEDI(Stillbirth, mummification, embryonic death, and infertility), brucellosis and parvo virus.

Acute leptospirosis, as described in calves, has been described in piglets but is rare.

Treatment and control are similar to cattle.


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