Treatment Methods and Prevention Measures for Swine Toxoplasmosis

Swine toxoplasmosis is a zoonotic infectious disease caused by Toxoplasma gondii. This disease is most commonly seen in pigs. Humans can contract the disease through wound contact or by eating raw meat infected with this disease. Therefore, conducting pre-slaughter quarantine and post-slaughter inspection for swine toxoplasmosis at designated slaughterhouses is of vital importance for safeguarding the development of the breeding industry and human health.

1 Pre-slaughter quarantine

Pigs suffering from swine toxoplasmosis show an elevated body temperature reaching 41-42°C, reduced or complete loss of appetite, nasal discharge, coughing or difficulty breathing, anemia, conjunctival congestion of the eyes, etc. The clinical symptoms are similar to those of swine fever and swine erysipelas, but there are no large hemorrhagic spots on the skin.

2 Post-slaughter inspection

The meat of pigs with acute toxoplasmosis shows incomplete bleeding, and the skin of the whole body is mostly purplish-red. Yellow clear fluid accumulates in the skin of both ears, neck, lower abdomen, limbs, buttocks, and tail.

2.1 Enlarged and hardened lymph nodes, mainly seen in the mesenteric lymph nodes, gastric lymph nodes, hepatic lymph nodes, and pulmonary lymph nodes, slightly swollen to the size of a chicken egg, especially the mesenteric lymph nodes. Generally, in the middle and posterior sections of the jejunum, 3-5 or more enlarged and hardened mesenteric lymph nodes can be seen. When cut open, they feel hard and brittle, and the cut surface is brick-red or grayish-red. In acute infection, all mesenteric lymph nodes show medullary swelling, with a yellowish-white cut surface and a yellowish-brown periphery, with a large amount of serous exudation, and edema in the surrounding interstitial tissue.

2.2 The liver generally shows cloudy swelling, with small petechial hemorrhages or congestion. The liver is enlarged and brittle, with yellowish-white or grayish-white necrotic spots of varying sizes.

2.3 The lungs show incomplete retraction, often with congestion and edema, expanded interstitium, and a grayish-white color. In acute infection, the lungs show severe congestion and edema, sometimes with hemorrhage, necrosis, and compensatory emphysema. A large amount of fluid flows from the cut surface, and the trachea contains red foam.

2.4 The spleen in acute infection is often enlarged 2-3 times, brownish or cherry-red in color, with several soybean-sized hemispherical protrusions on the surface. The cut surface is indistinct, and yellowish-white necrotic foci can sometimes be seen.

2.5 The kidneys generally only appear redder in color, occasionally showing cloudy swelling and a few petechiae or hemorrhagic spots. Sometimes petechiae are seen near the auricles or coronary groove.

3 Diagnosis

3.1 Differential diagnosis: The clinical symptoms and post-slaughter pathological changes of this disease are extremely similar to certain pathological changes of swine fever and swine erysipelas. Therefore, in differential diagnosis, the pathological changes of the spleen (several soybean-sized hemispherical protrusions on the surface) are mostly used, combined with other pathological changes, to make a diagnosis. Do not confuse it with swine fever to avoid misdiagnosis. Laboratory diagnosis can also be performed.

3.2 Laboratory diagnosis: Generally, the smear microscopic examination method is used. After collecting muscle, organ, or lymph node smears and allowing them to air-dry naturally, fix with methanol for 10 min, stain with 25-fold diluted Giemsa stain for 40 min, rinse with neutral distilled water, and examine under an 800x microscope. Under the microscope, various forms of Toxoplasma protozoa can be seen. The most common is a curved body with one end bluntly rounded and the other end pointed. A few have one end bluntly rounded and the other end pointed but arranged in a straight line. Some are bow-shaped, or bean-pod-shaped. Some have both ends bluntly rounded and are curved. Some are hammer-shaped, some are rod-shaped, with varying forms.

4 Disposal

4.1 Carcasses and internal organs of pigs with acute swine toxoplasmosis shall be destroyed.

4.2 After the diseased organs and lymph nodes are removed, they shall be used for industrial purposes or destroyed. The carcass and other internal organs shall be treated with high temperature.