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Proceedings of the First Symposium on Marsupials in New Zealand

Gross Lesions

Gross Lesions

The distribution of gross lesions as seen at post mortem of poisoned wild possums in three surveys is given in Table 1. These figures show that the lungs are the most commonly affected site (202/327 - 61.8% of cases). The superficial lymph nodes were affected on 203 occasions. As some possums would have lesions in more than one superficial lymph node the total number of possums with lesions in these sites would be somewhat less than 62.7%. Nevertheless, superficial lymph nodes would be the second most common site affected.

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Table 1. Distribution of gross lesions in poisoned wild possums.
SITE A. B. C. TOTALS
No % No % No % No %
Lung 21 80.1 81 55.1 100 65 202 61.8
Liver 12 46.2 28 19.0 20 13 60 18.3
Spleen 2 7.7 14 9.5 9 5.8 25 7.6
Kidney 2 7.7 18 12.2 6 3.9 26 7.9
Adrenal 2 7.7 3 2.0 - - 5 1.5
Axillary lymphnodes 2 7.7 46 31.3* 81 52.6* 129 39.4
Inguinal " " 4 15.4 17 11.6+ 28 18.2+ 49 14.9
Mediastinal " " 3 11.5 8 5.4§ 30 19.5§ 41 12.5
Mesenteric " " 7 26.9 27 18.4 31 20.1 65 19.8
Gastric " " 4 15.4 2 1.4 1 0.6 7 2.1
Hepatic " " 3 11.5 14 9.5 14 9.1 31 9.4
Iliac/sublumbar lymphnodes 1 3.9 5 3.4 5 3.2 11 3.3
Peripharyngeal/cervical lymphnodes - - 3 2.0 22 14.3 25 7.6
Total No. of possums 26 147 154 327
APossum tuberculosis survey - Waikato region 1974 (Lake 1974)
BPossums from Hohonu Mountain 1974 (Animal Health Division 1974)
CPossums from Buller and Inangahua counties 1974 (Cook 1974)

Lesions have also been recorded in splenic and renal lymph nodes, prostate and mammary glands, stomach, intestine and heart (Animal Health Division 1974, Cook 1974, Lake 1974). Bone infections also occur occasionally.

The distribution of lesions in experimentally infected possums is shown in Tables 2 and 3. Following subcutaneous inoculation on the medial aspect of the left thigh the nature and distribution of lesions at post-mortem resembles those seen in naturally infected wild possums. Intranasal instillation produced a less widespread distribution of lesions with involvement of somatic lymph nodes confined to the head and neck only (O'Hara et al. 1976).

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Table 2. Distribution of gross lesions in subcutaneously infected possums (O'Hara et al. 1976).

Table 2. Distribution of gross lesions in subcutaneously infected possums (O'Hara et al. 1976).

Table 3. Distribution of gross lesions in intranasally infected possums (O'Hara et al. 1976).

Table 3. Distribution of gross lesions in intranasally infected possums (O'Hara et al. 1976).

Somatic lymph node lesions are typically a soft fluctuating abscess with a diameter up to 4 cm containing a semi-liquid lime green pus. On occasions these abscesses open and form sinus tracts, discharging their contents. White to yellow nodules up to 2 cm in diameter are the most commonly seen lesions in visceral organs and lymph nodes. They may be multilobular and have a more page 167 caseous centre than a somatic lesion. In some possums miliary white lesions will be seen in the lungs, liver, spleen or kidneys. The lungs of other possums may have generalised grey-white consolidation of part of a lobe or lobes.