NAVLE Hemic and Lymphatic

Porcine Mycoplasma suis Infection Study Guide

November 14, 2026 20 min read
Mycoplasma suis (formerly Eperythrozoon suis) is a hemotrophic mycoplasma (hemoplasma) that causes infectious anemia of pigs (IAP), also known as porcine eperythrozoonosis.

Overview and Clinical Importance

Mycoplasma suis (formerly Eperythrozoon suis) is a hemotrophic mycoplasma (hemoplasma) that causes infectious anemia of pigs (IAP), also known as porcine eperythrozoonosis. This obligate erythrocyte parasite attaches to and invades red blood cells, causing extravascular hemolytic anemia. The disease is characterized by fever, icterus, anemia, and hypoglycemia, particularly in stressed or immunocompromised animals.

The organism is pleomorphic, measuring 0.8-1.0 micrometers in diameter, and appears as coccoid, rod, or ring-shaped structures on erythrocyte surfaces when viewed with Giemsa or Wright-Giemsa stains. M. suis cannot be cultured in vitro, making diagnosis challenging and requiring molecular methods for definitive identification.

Characteristic Description
Classification Hemotrophic mycoplasma (hemoplasma), Class Mollicutes
Size 0.8-1.0 micrometers (may be larger during acute infection)
Morphology Pleomorphic: coccoid, rod, or ring-shaped on RBC surface
Cell Wall Absent (lacks cell wall like all mycoplasmas)
Culture Cannot be cultured in vitro (uncultivable)
Host Specificity Highly species-specific to swine

Etiology

Organism Characteristics

High-YieldM. suis is an obligate, uncultivable bacterium. The inability to culture this organism means diagnosis relies on blood smear examination and PCR, and experimental studies require live animal models (often splenectomized pigs).
Route Mechanism
Iatrogenic Reuse of contaminated needles, surgical instruments, ear tagging, teeth clipping, tail docking
Vector-borne Hog louse (Haematopinus suis), mosquitoes, biting flies
Direct Contact Licking open wounds, cannibalism, fighting (ranking bites)
Vertical In utero transmission (transplacental) demonstrated experimentally

Epidemiology

Transmission

Risk Factors and Seasonality

  • Age: Young growing pigs (2-8 months) most clinically affected
  • Season: Summer outbreaks more common (increased vector activity)
  • Stress: Weaning, transport, mixing, concurrent disease, farrowing
  • Co-infections: PCVAD, PRRS, Salmonella, parasitism increase susceptibility
  • Carrier state: Recovered pigs remain lifelong carriers
NAVLE TipThe hog louse (Haematopinus suis) is the largest sucking louse of domestic animals (~6mm). Always consider louse control as part of M. suis prevention. Look for lice in the ears, neck folds, and inner legs of affected pigs.
Form Clinical Signs Key Features
ACUTE High fever (40-42°C) Severe anemia, pallor Icterus (jaundice) Anorexia, listlessness Hypoglycemia (seizures, coma) Petechiae, cyanosis of ears Life-threatening Common in young pigs Death in 1-3 days if untreated Triggered by stress
CHRONIC Mild anemia Poor growth/weight gain Rough hair coat Skin lesions, urticaria Ear tip necrosis Immunosuppression More common form Subclinical carriers Increased susceptibility to secondary infections
REPRODUCTIVE Agalactia (no milk) Weak/pale piglets at birth Increased stillbirths Delayed return to estrus Poor conception rates Acute signs often periparturient Sows may be subclinical until farrowing stress

Pathogenesis

The pathogenesis of M. suis infection involves multiple mechanisms leading to hemolytic anemia and metabolic derangements:

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