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
