Pathological lesions in spleen of Chinese spiny frog (Quasipaa spinosa) after Aeromonas hydrophila infection

doi:10.3969/j.issn.1004-1524.20240499

Acta Agriculturae Zhejiangensis ›› 2025, Vol. 37 ›› Issue (6): 1221-1232.DOI: 10.3969/j.issn.1004-1524.20240499

• Animal Science • Previous Articles Next Articles

Pathological lesions in spleen of Chinese spiny frog (Quasipaa spinosa) after Aeromonas hydrophila infection

REN Siyu(), WU Chunyan^*(), LIU Zhenkun, YANG Yanhui

College of Animal Science and Technology, Chongqing Three Gorges Vocational College, Chongqing 404155, China

Received:2024-06-07 Online:2025-06-25 Published:2025-07-08

Abstract

Abstract:

In order to explore the pathological lesions in spleen of Chinese spiny frog (Quasipaa spinosa) after haemorrhagic septicemia infection, Aeromonas hydrophila isolated from diseased Chinese spiny frog, which was identified as the pathogenic bacterium, was used to replicate haemorrhagic septicemia in health individual with body weight of (130±20) g. The challenge concentration was 1×10⁷ CFU·mL^-1 and the injected dose was 0.2 mL per frog. The spleen was selected as representative of the internal organs for clinical symptoms and dynamic pathological observation was carried out at 2 h, 4 h, 8 h, 12 h, 16 h, 24 h, 32 h, 40 h, 48 h, 60 h, 72 h, 96 h(4 d), 120 h(5 d), 144 h(6 d), 168 h(7 d) after infection, respectively. It was shown that the main clinical signs included lethargy and depression with increasing of the spleen index which was significantly (P<0.01) different between the control group and the infection group from 40 h to 5 d. The observation of dynamic pathological showed necrosis and reduction of lymphocytes and reticular cells in white pulp district with an increase of single melano-macrophage, and varying degrees of degeneration and necrosis in tunica. Especially, the typical pathological damage included severe necrosis in white pulp and disappearance of melano-macrophage centres (MMCs) with reticular fibre decomposition from 48 h to 72 h. The research indicated that under the stress of lethal septicemia, the splenic structure of the frog was disintegrated, the cell components were severely necrotic, and the structural basis of the immune organ was destroyed.

Key words: Quasipaa spinosa, Aeromonas hydrophila, haemorrhagic septicaemia, pathological lesions

CLC Number:

S948

REN Siyu, WU Chunyan, LIU Zhenkun, YANG Yanhui. Pathological lesions in spleen of Chinese spiny frog (Quasipaa spinosa) after Aeromonas hydrophila infection[J]. Acta Agriculturae Zhejiangensis, 2025, 37(6): 1221-1232.

Figures/Tables 8

Table 1 Gross dynamic pathology of spleen after SZW-003 infection

采样时间 Sample time	颜色 Colour	被膜 Capsule	质地 Character	大小 Size
2~4 h	深红Deep red	有光泽Glossy	柔软Soft	正常Normal
8~16 h	暗红Dull red	被膜紧张、浑浊The capsule of spleen was tense and muddy	松软Soft	轻微肿大Slight swelling
24~40 h	发黑Nigrescence	被膜紧张、无光泽The capsule of spleen was tense without gloss	松散Loose	肿大Swelling
48~72 h	暗黑Dark	被膜紧张、无光泽The capsule of spleen was tense without gloss	松散Loose	显著肿大Significantly enlarged
4~7 d	暗红Dull red	被膜无光泽The capsule of spleen was not glossy	松软Soft	肿大但趋于正常Slight swelling

Table 2 Spleen index after SZW-003 infection

t/h	脾体指数 Spleen index	t/h	脾体指数 Spleen index
0	0.108±0.019	40	0.320±0.103^**
2	0.120±0.011	48	0.293±0.054^**
4	0.121±0.024	60	0.321±0.114^**
8	0.108±0.036	72	0.311±0.083^**
12	0.199±0.037^*	96	0.231±0.073^**
16	0.194±0.050	120	0.208±0.043^**
24	0.212±0.039^*	144	0.168±0.036
32	0.177±0.035	168	0.190±0.082

Fig.1 Dynamic pathological changes of white pulp after SZW-003 infection (HE staining) a, Normal spleen showing the reticular cells (→)and lymphocytes()without pathological changes; b, 2-4 h after infection, hyperaemia was obvious in blood sinus of white pulp(→); c, 8-16 h after infection, necrosis of reticular cells(), and the pathological staining was not clear in lymphocytes(→)with neutrophilic granulocytes infiltration(); d, 24-40 h after infection, degeneration and necrosis of lymphocytes(→)and reticular cells(); e, 48-72 h after infection, serious necrosis of lymphocytes()and reticular cells(→)in white pulp with numerous debris(); f, 4-7 d after infection, the spleen showing hyperaemia with normal structure(→); g, Reticular cells (→)and lymphocytes()without pathological changes in the control group.

Fig.2 Dynamic pathological changes of red pulp after SZW-003 infection (HE staining) a, Normal spleen showing the red pulp without pathological change; b, 2-4 h after infection, slight hyperaemia in blood sinus(→); c, 8-16 h after infection, serious hyperaemia between the white pulp and red pulp(→); d, 24-40 h after infection, the red pulp showing broken fiber()with cells descrete, and degeneration of reticular cells like phagocyte(→); e, 48-72 h after infection,the spleen showing severe pathological injury with necrosis of lymphocytes ()and reticular cells(→); f, 4-7 d after infection, the spleen showing swellen reticular cells()and fiber(→)with normal structure; g, Spleen in the control group showing red pulp without pathological change.

Fig.3 Dynamic pathological changes of capsule after infection (HE staining) a, Normal spleen showing the capsule without pathological change; b, 2-4 h after infection, the spleen was normal; c, 8-16 h after infection,degeneration and swellen in capsule(→); d, 24-40 h after infection, the fiber structure was disorder with serious swellen in capsule(), and the reticular cell(→) presented degeneration and exfoliated under the capsule; e, 48-72 h after infection, the capsule(→) was significantly thinned with swellen and exfoliated reticular cells() under it; f, 4-7 d after infection, the capsule presented swellen(→); g, Spleen in the control group showing the capsule without pathological change.

Fig.4 Dynamic pathological changes of fiber in spleen after infection a, Uninterrupted elastic fiber in capsule in normal spleen(→), Tanake Victoria blue staining; b, 48-72 h after infection, reduced elastic fiber in capsule(→),Tanake Victoria blue staining; c, 48-72 h after infection, discontinuous light blue signal on the venous vessel wall(→), Tanake Victoria blue staining; d, Obvious reticular fiber without interruption in normal spleen(→), modified Gomori silver ammonia method; e, 48-72 h after infection, disordered reticular fiber in the blood vessel wall(→)and around it(), modified Gomori silver ammonia method; f, 48-72 h after infectin, the reticular fiber in red pulp dissolved and disappeared(), modified Gomori silver ammonia method; g, Moderate collagen fibers in red pulp of normal spleen with weaker signal(→), Masson trichrome staining; h, 48-72 h after infection, the collagen fibers dissolved in red pulp, Masson trichrome staining; i, 4-7 d after infectin, significantly enhanced blue signal in the red pulp (→), Masson trichrome staining; j, Uninterrupted elastic fiber in capsule of spleen in the control group(→), Tanake victoria blue staining; k, Obvious and uninterruputed reticular fiber of spleen in the control group(→), modified Gomori silver ammonia method; l, Moderate collagen fibers in red pulp spleen with weaker signal in the control group(→), Masson trichrome staining.

Fig.5 Dynamic pathological changes of melano-macrophages and melano-macrophage centres (MMCs) after infection a, MMCs in normal spleen were dense and clear in outline(),HE staining; b, MMCs in light blue()with a small amount of light yellow(→)in normal spleen, Perls staining; c, 8-16 h after infection, melano-macrophages and small MMCs increased obviously(), Perls staining; d, 24-40 h after infection, melano-macrophages and small MMCs increased obviously(), Perls staining; e, 24-40 h after infection, the MMCs presented histolysis(), HE staining; f, 48-72 h after infection, the spleen showed severe injury, the MMCs dissolved and disappeared, HE staining; g, 4-7 d after infection, the small MMCs increased(▲), and the MMCs presented mainly blue()with a small amount of light yellow(→), Perls staining; h, MMCs in spleen of the control group were dense and clear in outline(), HE staining; i, Fewer melano-macrophages in spleen of the control group(→), Perls staining.

Fig.6 Pathological changes of spleen in dying and survival Quasipaa spinosa (HE staining) a, Denegaration and necriosis of reticular cells()and lymphocytes(→)of dying Chinese spiny frog (Quasipaa spinosa); b, White pulp(▲)disappeared and red pulp presenting congestion with spleen cord rupture() of dying Chinese spiny frog; c, Red pulp showing hyperaemia() with swellen reticular cells(→), and MMCs increased(▲) in quantity in survival Chinese spiny frog; d, MMCs increased(▲) in quantity with normal white pulp of survival Chinese spiny frog.

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Pathological lesions in spleen of Chinese spiny frog (Quasipaa spinosa) after Aeromonas hydrophila infection

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