Quarantine Methods and Handling 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, carrying out ante-mortem quarantine and post-mortem inspection for swine toxoplasmosis at designated slaughterhouses is of vital importance for safeguarding the development of the breeding industry and human health.

1 Ante-mortem quarantine

Pigs suffering from swine toxoplasmosis show an elevated body temperature reaching 41-42°C, reduced or complete loss of appetite, runny nose, coughing or difficulty breathing, anemia, and conjunctival hyperemia, 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-mortem inspection

The meat of pigs suffering from acute toxoplasmosis shows incomplete bleeding. The skin over the whole body is mostly purplish-red. Yellowish clear fluid accumulation is present in the skin of both ears, neck, lower abdomen, limbs, buttocks, and tail.

2.1 Enlargement and induration of 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, 3-5 or more enlarged and indurated mesenteric lymph nodes can be seen in the middle and posterior segments of the jejunum. 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, interstitial expansion, 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 often on the surface. The cut surface is indistinct, and yellowish-white necrotic foci may sometimes be seen.

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

3 Diagnosis

3.1 Differential diagnosis: The clinical symptoms and post-mortem 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 often 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 carried out.

3.2 Laboratory diagnosis: Generally, the smear microscopy method is used. Samples of muscle, organs, or lymph nodes are collected and smeared, then air-dried naturally, fixed with methanol for 10 min, stained with 25-fold diluted Giemsa stain for 40 min, rinsed with neutral distilled water, and examined under an 800-fold microscope. Under the microscope, various forms of Toxoplasma protozoa can be seen. The most common form is a curved organism with one end bluntly rounded and the other end more pointed. A few have one end bluntly rounded and the other end pointed but straight; some are bow-shaped or kidney-bean-shaped; some have both ends bluntly rounded and are curved; some are hammer-shaped; some are rod-shaped, with varying forms.

4 Handling

4.1 Carcasses and internal organs of pigs suffering from 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 organs shall be treated with high temperature.