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Anaplasmosis in cattle (Proceedings)

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Aug 01, 2008

Definition/Etiology

Infectious, transmissible disease of cattle, sheep and goats.

Caused by the Rickettsial organism, Anaplasma marginale in cattle.

A. ovis in sheep/goats

Epidemiology

Most prevalent of the tick borne diseases of cattle

Has been reported in at least 40 states, and is considered endemic to certain areas of the US

Maintained in a population by the presence of a good vector and subclinical carrier animals.

Clinical Signs

Dependent upon:

Age at time of infection

Breed differences in susceptibility

Virulence of the strain

Young calves (6-9 months)

Asymptomatic to mild

Adult cattle

Severity tends to increase with increasing age

4 stages

1. Incubation – 21-45 days

2. Acute disease – signs appear when approximately 1% of red cells or greater are infected.

3. Convalescent stage – 3-4 weeks

4. Carrier stage – for life?

1. Animals are generally asymptomatic during the incubation phase.

2. Acute disease can be characterized by the following:

Fever – 103-106°F for 24-48 hrs, then drops to normal or below

Anorexia

Acute death

Drop in milk production

Lethargy

Rumen stasis

Dry muzzle

Aggressiveness – hypoxia?

Staggering gait – weakness from anemia/hypoxia

Tachycardia

Pale and/or icteric mucous membranes

Constipation with dark brown, mucus covered feces (sometimes I think it is a bronze tinge)

Dark yellow urine

(NO HEMOGLOBINURIA AS THIS IS AN EXTRAVASCULAR HEMOLYTIC EVENT)

Abortion

3. Convalescent period characterized by weight loss, icterus

4. Asymptomatic

Sheep/Goats

Often asymptomatic, but can be severe enough to cause signs similar to infection with cattle.

Clinical Pathology

PCV/total protein:

Acute phase – PCV falls dramatically within the first 24 to 48 hrs. May be as low as 6-10% upon presentation. Total protein is normal (hemolytic anemia). Organism can by detected in peripheral blood films during this phase (dif-quick stain). After anemia is present for several days, the number of organisms detected decreases and signs of regeneration are predominant (polychromasia, reticulocytosis, anisocytosis, basophilic stippling)

Carrier stage – organism is not reliably detected due to extremely low numbers present.

Serology – not reliable for acute disease, but can detect carriers.

Serum Chemistry:

Hyperbilirubinemia

Urinalysis:

Hyperbilirubinuria