Diseases of the guinea pig

Antibiotic toxicity. Guinea pigs and hamsters are highly susceptible to the toxic effects of many of the commonly used antibiotics. Toxicity results from overgrowth of the normal gram-positive cecal flora by gram-negative rods. This causes fatal enterocolitis, with diarrhea and death in 3 to 7 days. Antibiotics with an activity spectrum directed primarily against gram-positive organisms (e. g., penicillin, lincomycin, eryth­romycin, tylosin) should not be used in guinea pigs and hamsters. Broad-spectrum antibiotics should not be used oral­ly because of their direct effect on the intestinal flora, but may be used parenterally with caution.

Metastatic calcification occurs most often in male guinea pigs over a year or age. Signs include slow weight gains, stiff joints and high mortality. At necropsy, calcium deposits are seebn in the lung, liver, heart, aorta, stomach, colon, kidney, joints and skeletal muscles. There are conflicting reports concerning the etiology; however, most investiga­tors agree that when animals are fed diets low in magnesi­um and potassium, the calcificlesions increase with the phos­phorus content of the ration. It is believed that hyperphos­phatemia results from the inability of the guinea pig to conserve fixed bases by excreting ammonia in the urine; thus, the low-base reserve impairs normal urinary excretion of phosphorus. The condition may be aggravated by increasing the vitamin D content of the ration beyond 6 IU/gm. The condition may be minimized or prevented by feeding diets that contain adequate magnesium (0.35 per cent), a calciumiphosphorus ratio of 1.3 to 1.5:1, and not more than 6 IU of vitamin D per gram.

Scurvy. (Vitamin С deficiency): Guinea pigs require a dietary supply of ascorbic acid (vitamin C) because they lack the enzymes necessary for conversion of L-gulonolactone to L-ascorbic acid. Signs of vitamin С deficiency are unsteady gait, painful locomotion, hemorrhage from gums, swelling of costochondral junctions and emaciation. Lesions include hemorrhages in the subcutis, around joints and on all serosal surfaces. The condition may be prevented by providing 1 to 3 mg ascorbic acid per 100 mg body wt daily. Commercial guinea pig diets contain vitamin С which is stable for 3 months after milling. Marginal diets should be supplemented with greens or vegetables high in vitamin C.

Muscular dystrophy. Guinea pigs are exquisitely sensi­tive to dietary deficiency of vitamin E.

Signs are stiffness, lameness and refusal to move. Micro­scopic lesions include coagulative necrosis, inflammation and proliferation of sarcolemmal nuclei in skeletal muscle. Diets should contain 3 to 5 mg of vitamin E per 100 mg.

Ringworm is a common mycotic infection in guinea pigs, usually caused by Trychophyton mentagrophytes or Microsporum gypseum. It causes characteristic, crusty, flak­ing lesions on the skin. Facial lesions are usually prominent. Diagnosis is based on characteristic lesions and cultural and microscopic identification of the causative organism. The disease is usually self-limiting if good husbandry and sanita­tion are maintained. Long-term feeding of griseofulvin is effective. Isolated skin lesions may be treated effectively with tolnaftate cream. The disease is contagious to man.