Anaplasmosis: Symptoms, Types, Causes and Treatment

Anaplasmosis is a tick-borne disease that affects both humans and animals, caused by the bacteria of the genus Anaplasma. While often overshadowed by other tick-borne illnesses like Lyme disease, anaplasmosis is an emerging threat in many parts of the world. Understanding its symptoms, various types, causes, and treatment options is crucial for timely diagnosis and effective management. In this article, we’ll take a comprehensive look at anaplasmosis, guided by the latest research findings.

Symptoms of Anaplasmosis

Anaplasmosis can present with a variety of symptoms, many of which are nonspecific and resemble other infectious diseases. Recognizing these signs, particularly in people or animals with a history of tick exposure, is essential for early intervention.

Symptom	Frequency/Severity	Notes/Details	Source(s)
Fever	Common	Usually high, can persist for days	1, 2, 3, 4, 13
Malaise	Common	General feeling of discomfort or unease	2, 13
Headache	Frequent	Sometimes severe	2, 13
Myalgias	Frequent	Muscle aches	3, 13
Thrombocytopenia	Common	Low platelet count, can be severe	1, 2, 4, 13
Leukopenia	Common	Low white blood cell count	2, 13
Elevated LFTs	Frequent	Liver enzyme abnormalities	1, 3, 13
GI symptoms	Occasional	Nausea, vomiting, decreased appetite	4, 13
Neurological	Rare	Stroke-like symptoms, confusion	2, 7
Pulmonary	Rare	Cough, pneumonitis	3
Rash	Rare	Occasionally present	13
Anemia	Sometimes	More common in animal cases	1, 12

Table 1: Key Symptoms of Anaplasmosis

Overview of Common Symptoms

The clinical picture of anaplasmosis is often dominated by flu-like symptoms, such as fever, malaise, headache, and muscle aches. These symptoms can make early diagnosis challenging, as they overlap with other infectious and inflammatory conditions 2 13.

Hematological and Laboratory Findings

A hallmark of anaplasmosis is the presence of cytopenias—especially thrombocytopenia (low platelets) and leukopenia (low white blood cell count). Many patients also exhibit elevated liver enzymes (LFTs), which can signal organ involvement 1 2 3 13.

• Thrombocytopenia: Frequently observed, can be marked and lead to bleeding complications if severe. 2
• Leukopenia: Results in increased infection risk.
• Elevated LFTs: Suggests hepatic involvement, not always present but common.

Less Common and Severe Manifestations

While most cases are mild to moderate, some patients, especially the elderly or immunocompromised, may develop severe complications:

• Neurological symptoms: Such as stroke-like weakness or confusion, though rare, have been reported 2.
• Pulmonary involvement: Cases presenting with cough or pneumonitis have been described 3.
• Hemophagocytic lymphohistiocytosis (HLH): A rare but life-threatening immune reaction 7.
• Anemia: Particularly prominent in animal cases, such as cattle, but can occasionally occur in humans 1 12.

Symptom Onset and Duration

Symptoms typically appear 1–2 weeks after a tick bite and may persist if untreated. In some cases, especially those with delayed diagnosis, the disease can progress to multi-organ involvement or severe complications 2 7.

Types of Anaplasmosis

Anaplasmosis is not a single disease but a group of related conditions caused by different Anaplasma species. Understanding the distinct types is key for accurate diagnosis and targeted management.

Type	Host	Main Vector/Tick	Geographic Distribution	Source(s)
Human Granulocytic	Humans	Ixodes ticks	North America, Europe, Asia	5, 9, 13
(A. phagocytophilum)
Bovine Anaplasmosis	Cattle	Rhipicephalus, Dermacentor	Worldwide (esp. tropics)	5, 8, 10
(A. marginale)
Ovine/Caprine	Sheep, goats	Rhipicephalus bursa	Mediterranean, Africa	1, 6, 10
(A. ovis)
Canine/Feline	Dogs, cats	Various tick species	Global	4, 6
(A. platys, A. phagocytophilum)
Emerging/Other	Various (wildlife, humans)	Various ticks	Region-specific	6, 10

Table 2: Major Types of Anaplasmosis

Human Granulocytic Anaplasmosis (HGA)

• Agent: Anaplasma phagocytophilum
• Presentation: Acute febrile illness, often with cytopenias and elevated liver enzymes 9 13.
• Vector: Primarily Ixodes scapularis (Northeastern US) and Ixodes pacificus (California) 13.
• At-risk populations: Elderly, immunocompromised, those exposed to wooded or grassy areas 2 11.

Bovine Anaplasmosis

• Agent: Anaplasma marginale
• Presentation: Progressive anemia, fever, jaundice, weight loss in cattle; can be fatal if untreated 5 8 12.
• Vector: Multiple tick genera and mechanical transmission by biting flies or contaminated instruments 8 10.
• Economic impact: Significant losses in cattle industry globally 5 8.

Ovine/Caprine Anaplasmosis

• Agent: Anaplasma ovis
• Hosts: Sheep, goats, wild ruminants 1 6.
• Human infection: Rare, but documented case reports exist 1.
• Vectors: Commonly Rhipicephalus bursa ticks 1.

Canine and Feline Anaplasmosis

• Agents: A. phagocytophilum and A. platys most commonly in pets 4 6.
• Presentation in pets: Fever, lethargy, pain, mild hematological changes; rarely severe 4.

Emerging and Other Types

• Other species: Novel strains and types are being identified in wildlife, ticks, and occasionally humans (e.g., A. capra, A. centrale, etc.) 6 10.
• Zoonotic potential: Some animal strains may occasionally infect humans; ongoing research is clarifying these risks 1 6.

Causes of Anaplasmosis

The underlying cause of anaplasmosis is infection by Anaplasma bacteria, which are obligate intracellular organisms primarily transmitted by ticks. Understanding how these bacteria spread and the risk factors for infection is vital for prevention.

Cause/Factor	Description	Risk Population/Setting	Source(s)
Tick Bites	Main transmission route	Humans, domestic animals	5, 8, 9, 13
Blood Transfusion	Possible, especially in animals	Cattle, rare in humans	5, 8, 10
Mechanical Fomites	Contaminated tools/equipment	Cattle (dehorning, tagging)	8, 10
Reservoir Hosts	Wildlife (deer, rodents, birds)	All regions	1, 6, 10
Geographical Hotspots	Endemic regions (wooded, rural)	NE US, Midwest, Mediterranean	11, 13
High-Risk Activities	Outdoor work, recreation	Hikers, farmers, veterinarians	5, 11, 13

Table 3: Main Causes and Risk Factors for Anaplasmosis

Tick-Borne Transmission

• Ticks as Vectors: The primary route of anaplasma infection in both humans and animals is via tick bites. Ixodes species are the main vectors for human disease, while Rhipicephalus, Dermacentor, and Amblyomma are important in veterinary settings 5 8 9 13.
• Seasonality: Most cases occur between late spring and early fall, coinciding with tick activity 2 11.

Other Transmission Routes

• Blood Transfusion: Rare but possible, especially among animals, due to the persistence of the bacteria in blood 5 8.
• Mechanical Transmission: In cattle, contaminated needles or tools used during procedures can spread infection 8 10.

Reservoirs and Environmental Factors

• Wildlife Reservoirs: Deer, rodents, and even birds can serve as reservoirs, maintaining the bacteria in the ecosystem 1 6 10.
• Endemic Regions: Exposure risk is highest in certain geographic hotspots, such as the Northeast and Midwest United States, Mediterranean basin, and parts of Africa 11 13.

Human-Specific Risk Factors

• Outdoor Activities: People who live in or frequently visit wooded or grassy areas, or those with occupational exposure (e.g., forestry workers, farmers, veterinarians), are at increased risk 5 11 13.
• Age and Immunosuppression: Elderly individuals and those with weakened immune systems are more susceptible to severe disease 2 7.

Treatment of Anaplasmosis

Timely treatment is essential for reducing morbidity and preventing complications. While several antibiotics have been used historically, tetracyclines remain the cornerstone of therapy for both humans and animals.

Treatment	Indication	Effectiveness/Notes	Source(s)
Doxycycline	First-line (humans/animals)	Rapid symptom resolution, oral/IV options	1, 2, 4, 5, 7, 13
Oxytetracycline	Veterinary use	Effective in animals, parenteral admin	12, 15
Chlortetracycline	Animal control	Oral, controls but may not clear infection	15
Supportive Care	Severe/complicated cases	IV fluids, transfusions, organ support	7
Immune Modulation	HLH or severe cases	Steroids, anakinra (rare, specific cases)	7
Prevention	Tick avoidance, vector control	No human vaccine; animal vaccines limited	5, 8, 10

Table 4: Current Treatment Options for Anaplasmosis

Antibiotic Therapy

• Doxycycline: The gold standard for both human and animal anaplasmosis. Rapid clinical improvement is usually seen within 24–48 hours 1 2 4 5 13.
  • Humans: 100 mg orally twice daily, typically for 10–14 days, or at least 3 days after fever resolves 13.
  • Animals: Doxycycline and oxytetracycline are both used; oxytetracycline is common in cattle, administered by injection 12 15.
• Chlortetracycline: Used in animals for control but may not reliably eliminate persistent infection 15.

Supportive Measures

• Severe Cases: Hospitalization, intravenous fluids, blood transfusions, and intensive care may be required for complications such as severe anemia, organ failure, or HLH 7.
• Immune Modulation: In rare instances of immune-mediated complications like HLH, corticosteroids and immunomodulatory drugs (like anakinra) have been used alongside antibiotics 7.

Challenges and Limitations

• Persistent Infection: In cattle, current tetracycline regimens may not always fully clear the infection, leading to persistent carriers 15.
• Delayed Diagnosis: Delay in starting treatment, often due to misdiagnosis, is associated with worse outcomes, especially in vulnerable populations 2 7.

Prevention and Control

• No Human Vaccine: Vaccines are available for animals in some regions but not universally effective; there is no human vaccine 5 8 10.
• Tick Control: Avoiding tick exposure, prompt tick removal, habitat management, and vector control are the main preventive strategies 5 8 10.
• Reservoir Management: Minimizing contact with wildlife reservoirs and maintaining tick-free herds in livestock are important for animal health 10.

Conclusion

Anaplasmosis is a complex and evolving disease that requires awareness, early recognition, and timely management to reduce its impact on human and animal health.

Key Takeaways:

• Symptoms are often nonspecific—fever, malaise, cytopenias, and elevated liver enzymes are common, but severe and rare complications can occur.
• Types of anaplasmosis depend on the Anaplasma species and host affected, with A. phagocytophilum and A. marginale being the most clinically significant for humans and cattle, respectively.
• Causes center on tick-borne transmission, but mechanical and reservoir-related factors also play a role, especially in animals.
• Treatment with doxycycline or related tetracyclines is highly effective if started promptly, but persistent infection in animals and severe complications in humans require additional attention.

For both clinicians and the general public:

• Recognize the risk in endemic regions and after possible tick exposure.
• Early diagnosis and treatment are crucial for optimal outcomes.
• Prevention remains focused on tick avoidance and vector control, as vaccines are not widely available.

Staying informed and vigilant is the best defense against this emerging tick-borne threat.