Lecture #41

Recognize the clinical significance and pathologic spectrum of parasitic diseases caused by hemo-coccidia in both companion animals and livestock.
- Understand that these parasites invade and mechanically destroy blood cells in host species.
Associate and identify the diagnostic stage, morphology, host distribution, and proper scientific names:
  - Hepatozoon: Found in leukocytes and bone marrow.
  - Babesia: Found in red blood cells of cattle, horses, dogs, and various other host species.
  - Theileria: Found in erythrocytes and macrophages of domestic and wild cattle/ungulates.
  - Cytauxzoon: Found in erythrocytes and macrophages of domestic and wild felines.
Relate the infective stages and basic modes of transmission with occurrence in infected and susceptible hosts.
- Sporozoites: Transmitted via the bite of infected ticks during their blood meal (e.g., Babesia, Theileria, Cytauxzoon) or by ingestion of ticks (e.g., Hepatozoon).
Apply knowledge of the lifecycle to diagnose infections and manage the risk of parasitic diseases.
- Disease expression relies on unlimited asexual replication in the vertebrate intermediate host.
- Ticks serve as the definitive host for sexual replication.
Recall general chemotherapies for the treatment of infected animals and prevention measures.

Intestinal Coccidia:
  - Eimeria
  - Cystoisospora
  - Toxoplasma
  - Neospora
  - Sarcocystis
Blood Coccidia:
  - Hepatozoon
  - Babesia
  - Cytauxzoon

Dixenic Organisms (Two hosts):
- Hemospordia (Malarial parasites): e.g., Plasmodium, Leucocytozoon
Monoxenic Organisms (One host):
- Cryptosporidia & other hematozoa (e.g., Babesia, Theileria, coccidia)
General Features of Apicomplexans:
- Possess a complete apical complex (conoid, rhoptries, micronemes).
- Obligate parasites.

Disease caused by Haemogregarine parasites in the genus Hepatozoon.
Significant host range of approximately 46 vertebrate species, with a notable distribution in reptiles (over 120 species in snakes).
Disease results from asexual replication of the parasite in leukocytes located in bone marrow, spleen, and to a lesser extent, the liver of the intermediate host (dogs).
Ticks are the definitive hosts where sexual reproduction takes place.
Dogs become infected by ingesting ticks containing mature oocysts in the hemocoel.

Stages of Infection:
  1. Sporozoites penetrate the gut wall.
  2. Mature oocyst and invade various tissues (e.g., skeletal muscle, leukocytes).
  3. The dog ingests the infected vector during tick feeding.
  4. Sexual reproduction occurs in the tick.
  5. Gamonts develop within neutrophils and monocytes.
  6. Ticks infect dogs by ingestion of gamonts found in the circulating leukocytes.

Old World Hepatozoonosis characterized by a long-term host association.
Distribution is worldwide; disease in infected dogs is usually milder than Hepatozoon americanum.
Natural infections in U.S. dogs are typically asymptomatic due to age-associated immunity (greater than 4 to 6 months old).
Dogs can develop transient fever, skeletal pain, and recumbency in severe cases.
Low parasitemia is noted except in severe cases with 100% of neutrophils infected.

American Hepatozoonosis confirmed as a distinct species via PCR sequence analysis.
Dogs become infected by ingesting infected Amblyomma maculatum ticks.
Disease severity is greater compared to H. canis; meronts asexually replicate in host cells within striated muscle.
Developing organisms remain protected in a cyst formation and free merozoites provoke an inflammatory response.

Symptoms include fever, lethargy, mucopurulent ocular discharge, neutrophilic leukocytosis, non-regenerative anemia, stiff gait, myositis, progressive muscle weakness, and head muscle atrophy.
Diagnosis involves muscle biopsy and serologic/PCR testing.

Lifelong infection is common in dogs; treatment is aimed at disease control but is not curative.
Recommended medications include:
  - Trimethoprim-sulfadiazine (15 mg/kg, PO, BID)
  - Clindamycin (10 mg/kg, PO, TID)
  - Pyrimethamine (0.25 mg/kg, PO, SID)
Daily therapy with Decoquinate (10-20 mg/kg, PO, BID) has shown protective effects against relapse.
Effective prevention strategies encompass avoiding tick exposure and monitoring predation on paratenic hosts (Amblyomma maculatum).

Asexual replication occurs in tissues and blood cells of mammalian intermediate hosts, with sexual reproduction occurring in ticks.
Piroplasms: Parasite stages in blood are pyriform, round, amoeboid, and rod-shaped.

Associated with non-regenerative anemia due to destruction of red blood cells.
Unlimited asexual replication is noted; there are at least 18 species worldwide.

Distribution primarily in Africa, Mediterranean, and Asia; responsible for conditions such as East Coast Fever and Egyptian Fever.

Formerly known as Theileria felis; causes a disease characterized by asexual replication in macrophages, causing fatal blockage of blood flow in cats.

Notable protozoan species found in red blood cells of hosts such as dogs (B. canis, B. gibsoni) and cattle (B. bigemina, B. bovis).
Transmission occurs primarily through the blood meal of infected ticks (e.g., Ixodes scapularis).

Major pathologies include pyrexia, anemia, leukocytosis, splenomegaly, and vomiting associated with helminthic infections in hosts.
B. canis: Generally non-pathogenic except in puppies; B. gibsoni: Can vary from subclinical to acute fatal cases.

Diagnosis through blood smears, serology for IgG antibodies, and PCR.
Treatment traditionally relies on Imidiocarb with a shift towards combination therapies (e.g., Azithromycin, Atovaquone).
Key prevention strategies include tick control and avoiding contact with known carriers.

Caused by Theileria orientalis, with significant importance in cattle production.
Transmissible through ticks:
- Clinical symptoms include fever, anemia, jaundice, and reduced production.
- Management: Limited treatment options exist; control mainly relies on vector management.

All hemo-coccidian parasites cause disease through mechanism of invasion and destruction of blood cells in host species, from Hepatozoon in leukocytes to Babesia in red blood cells.
Sporozoites are primarily transmitted via tick bites, except for Hepatozoon, which is ingested.
Disease expression relates to asexual replication in vertebrate hosts, with ticks facilitating sexual replication.