Anaplasmosis: The Summer Disease

Why Anaplasmosis Should Be on Every Rancher's Radar

Anaplasmosis is a tick-borne blood disease that hits Texas and Gulf Coast herds hard, both in animal losses and dollars. Often called "tick fever" or "yellow bag," it destroys red blood cells and causes severe anemia that can kill, especially in adult cattle. What makes it particularly dangerous is that recovered animals stay carriers for life, keeping the disease cycling through your herd.

Anaplasmosis Basics

The Causative Agent

The organism that causes anaplasmosis infects red blood cells but cannot survive outside a host or vector, meaning there is no environmental persistence. It requires direct transfer from one animal to another through blood.

How Anaplasmosis Spreads

``` INFECTED CARRIER ANIMAL (contains infected red blood cells) ↓ TRANSMISSION VECTOR (tick, biting fly, or contaminated equipment) ↓ SUSCEPTIBLE ANIMAL (organism enters bloodstream) ↓ INCUBATION (2-5 weeks) (organism multiplies in red blood cells) ↓ CLINICAL DISEASE (RBC destruction → anemia) ```

Transmission Routes

The Carrier Problem

Once an animal recovers from anaplasmosis, it becomes a lifelong carrier. The animal appears healthy and shows no outward signs of infection, but its blood can still transmit the disease. Roughly 75% of cattle in endemic areas are carriers, and there is no way to eliminate carrier status once it takes hold.

Recognizing Anaplasmosis

Who Gets Sick?

Clinical Signs

Early signs include depression, lethargy, separation from the herd, and fever ranging from 104-107 degrees F (40-41.5 degrees C).

As the disease progresses, cattle show weakness, rapid breathing to compensate for anemia, decreased milk production in dairy animals, and noticeable weight loss.

In severe cases, look for "yellow bag" (yellow coloring of the udder), extreme weakness or inability to rise, dark urine, collapse and death, and occasionally aggressive behavior caused by brain hypoxia.

Laboratory Findings

Diagnosis

Clinical Suspicion

Suspect anaplasmosis when you see fever combined with anemia and jaundice during summer or fall (peak tick season), especially if there is a history of tick exposure or known carriers in the herd.

Differential Diagnosis

Confirming Diagnosis

Collect whole blood with EDTA for PCR testing and blood smear examination. Pull serum for antibody testing and submit samples to a diagnostic lab promptly.

Treatment

Tetracycline Antibiotics

Treatment Protocol

• Minimize stress by moving the animal gently, since exercise can be fatal in anemic cattle.
• Administer antibiotics, typically oxytetracycline IM or IV.
• Provide supportive care including shade, water access, quality feed, and rest with no handling, moving, or added stress.
• Blood transfusion may be necessary in severe cases and should be handled by a veterinarian.
• Monitor response, as cattle should improve within 24-48 hours.
• Repeat treatment as needed based on clinical response.

Critical Warning: Avoid Stress

Anemic cattle have reduced oxygen-carrying capacity and cannot tolerate exertion. Treat the animal where it is standing if at all possible. If you must move it, go very slowly and stay out of the hot parts of the day.

Blood Transfusion

Cross-matching is preferred but not always practical in the field. Donors should test negative for anaplasmosis, and transfusion is usually a veterinarian procedure.

Prevention Strategies

1. Tick Control

2. Fly Control

Use the same methods you would for general fly control. Biting flies are a significant mechanical vector for anaplasmosis, so consistent fly management during summer months adds another layer of protection.

3. Equipment Sanitation

4. Chlortetracycline Feeding

Feeding chlortetracycline at 0.5-2 mg/lb body weight daily in mineral or supplement during tick season (4-6 months) suppresses infection but does not eliminate carriers. Factor in the cost of medication and withdrawal times for slaughter when deciding whether this approach fits your operation.

5. Vaccination

Killed vaccines are available and considered safe, though annual boosters are needed. Vaccines reduce disease severity but do not prevent infection or carrier status. In other countries, A. centrale is used as a live vaccine that causes mild infection followed by immunity.

6. Herd Management

Managing Carrier Animals

The Dilemma

Treatment only clears clinical disease. Low-level infection persists in recovered animals, and each carrier is a potential source for transmission to other cattle in the herd.

Options for Carriers

The most practical approach for most operations is to accept carrier status and focus on preventing clinical disease. Culling carriers gets expensive fast if many animals are affected and may not pencil out. Attempting to clear infection with multiple treatments is not standard practice.

Working with Carrier Herds

Focus your efforts on preventing clinical disease through tick control. Let calves become infected while they are young enough to handle it well, and protect adult cattle from the added stress of reinfection.

Seasonal Considerations in Texas

Risk Calendar

High-Risk Scenarios

Watch for trouble when introducing carrier cattle to a clean herd, during peak tick season in endemic areas, after shipping (stress can trigger relapse in carriers), and during hot weather when fly activity spikes.

Economics of Anaplasmosis

Costs of Disease

Prevention Costs

ROI Calculation

Consider a herd of 100 cows in an endemic area. Without prevention, assume 5% clinical cases (5 cows). If 2 die at $1,500 each, that is $3,000 in death losses. Treating the other 3 at $50 per head adds $150, bringing total losses to $3,150. With a solid prevention program, clinical cases drop to 0-1 per year, and losses fall to $0-1,500. In a bad year, that net benefit is significant.

Bottom Line

Age is the single biggest risk factor. Adult cattle over 3 years old face the highest mortality, and first exposure as a mature animal is the most dangerous scenario of all. Tick control is your primary line of defense in endemic areas, and it should run from spring through fall without gaps.

Anemic cattle absolutely cannot tolerate exertion, so treat infected animals where they stand whenever possible. Every recovered animal remains a lifelong carrier, and there is no way to cure that status. The silver lining is that young calves develop immunity with only mild disease, so allowing calf-hood exposure actually protects your herd long-term.

On the equipment side, changing needles between every animal is one of the simplest and most effective ways to stop mechanical transmission. Peak risk in Texas runs through the summer months, so seasonal awareness and proactive planning make a real difference. When you do catch clinical cases, tetracyclines work well and early treatment is usually effective.

Related Resources

• 5.4.6 Tick-Borne Disease Prevention
• 5.4.4 External Parasites: Flies, Lice, Ticks
• 5.5.6 When to Call the Vet Flowchart
• 5.3.2 Core Vaccines for Texas Cattle