A carcass of female cross bred piglet aged 20 days from an organised swine farm, IVRI was presented for necropsy examination. At necropsy, multiple liver abscess covering entire surface of liver was observed and upon incision creamy white pus oozed out from the cystic spaces. Spleen was enlarged and congested. Histopathological changes in liver included disorganization and distortion of the hepatic cords with degenerative and necrotic changes of the hepatocytes. Abscess was characterised by heavy infiltration of polymorph nuclear cells and severe haemorrhages in hepatic parenchyma. Necrotic areas were also infiltrated with mononuclear cells and surrounded by connective tissue capsules. Other significant changes were hyperplasia of the biliary duct epithelial cells, infiltration of neutrophils in the spleen and lungs. Bacteriological examination of liver sample revealed both P. aeruginosa and E.coli.
The world of infectious diseases is currently dominated by multidrug-resistant pathogens such as methicillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa, or Acinetobacter species and novel panresistant strains. So research and scientific publications are largely targeted towards such pathogens (Christou et al., 2011). Liver is considered to be the most important organ for mammalian metabolism thus any disturbance in this organ will reflect on the general health causing great economic losses in animal production (Blood et al., 1989). Liver lesions are common and they indicate the presence of disease in other organs and systems as the liver acts as a catchment for the vast absorptive area of the gut, with all its resident microorganisms (Kelly et al., 1985). Liver abscess is a major economic problem in meat industry due to condemnation of edible part of carcass. The hepatic system is particularly susceptible to abscesses because it receives blood from various sources, encompassing the hepatic artery, the portal system and the umbilical vein in fetus and neonate. Entry via portal vein is most common route (Nagaraja et al., 1998). Bacteria such as Fusobacterium necrophorum, Escherichia coli, Staphylococcus sp, Pasteurella sp., Streptococcus sp., Corynebacterium sp., Moraxella sp., Pseudomonas sp. and Clostridium sp. have been isolated by several workers from the hepatic abscesses of cattle, sheep and goats (Tehrani et al., 2012, Ghadrdan-Mashhadi et al., 2006). In lambs septicemia or extension of an umbilical vein infection can cause liver abscesses (Fetcher et al., 1983). E. coli is the universal predominant facultative organism in the gastrointestinal tract and isolated from liver abscesses worldwide. The multiple liver abscesses in case of large white Yorkshire pig is due to E. coli have been reported by (Kumar et al., 2014). Out of 56 cases of suppurative hepatitis, bacteriological examination showed the highest occurrence of E. coli i.e.12 (21.48%) and Pseudomonas (1.78%) in case of sheep and goats (Madhav et al., 2015). So keeping in view of the above, the present report describes the histopathological and bacteriological study of multiple hepatic abscesses in crossbred piglets.
Material and Method
A carcass of female cross bred piglet of aged 20 days from a swine farm was presented for the necropsy examination. Grossly liver was enlarged with multiple white nodules containing pus in all the lobes of liver (Fig. 1).
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Fig. 1: Enlarged liver with multiple white nodules containing pus, gross
Upon incision of liver, creamy white pus was discharged from the cystic spaces which were surrounded by fibrous capsules. Liver, spleen and diaphragm showed adhesions with each other. The tissues were collected in 10 percent neutral buffered formalin and paraffin sections were prepared and stained with haematoxylin and eosin stain as per the standard procedure. Bacteriological isolation was done on nutrient agar, blood agar and MacConky agar from liver specimens. The pure individual colonies when stained with Gram’s stain revealed presence of Pseudomonas aeruginosa and E. coli as Gram negative rod shaped organisms in the specimens. Biochemical tests like catalase, oxidase, urea, nitrate, citrate, gelatin, malonate and hydrogen sulphide were also carried out.
Results and Discussion
Bacteriological isolation was done on nutrient agar from liver specimen and it showed colonies which were surrounded by bluish green coloration and in blood agar it showed β haemolytic colonies suggestive of Pseudomonas aeruginosa. E. coli was also isolated on blood agar characterized by non haemolytic colonies and on MacConkey agar characterized by pink colonies which is in accordance with Silva et al., 1980. The pure individual colonies when stained with grams stain revealed Gram negative rod shaped organisms for both P. aeruginosa and E. coli. Isolate was positive for catalase, oxidase, urea, nitrate, citrate, gelatin, malonate and negative for hydrogen sulphide with both positive and negative for Indole by Pseudomonas aeruginosa. The cultural characteristics and biochemical tests of Pseudomonas aeruginosa were in accordance to Litovchenko et al., 1981.
Histopathological examinations of liver specimen showed disorganization and distortion of the hepatic cords with necrosis and degenerative changes of the hepatocytes. Similar observations have been reported in multiple abscess of goat (Sonawane et al., 2016). Necrosed hepatocytes with infiltration of mononuclear cells and histocytic cells surrounded by fibrous tissues were also seen. In the present study abscess was characterised by severe infiltration of degenerated and dead polymorphonuclear neutrophils in the sections of liver (Fig. 2), similar observations has been reported in case of hepatic abscess of Herrik sheep (Tehrani et al., 2012) and in multiple hepatic abscess of large White Yorkshire pig due to E. coli infections (Kumar et al., 2014).
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Fig. 2: Hepatic abscess characterised by severe infiltration of dead and degenerated polymorphonuclear neutrophils replacing hepatocytes with infiltration of mononuclear leukocytes, H&E, 400x
Disorganisation of hepatic chords and severe haemorrhages in hepatic parenchyma were observed. Infiltration of neutrophils in the spleen and interalveolar septa thickening due to infiltration of mononuclear cells along with neutrophils were found in the lungs.
The extensive damage to the liver was caused by multiple abscesses due to Pseudomonas aeruginosa and E. coli infection that lead to systemic spread of infections to other internal organs. This might have caused the death of the crossbred piglet.
The authors gratefully acknowledge and thank Indian Council of Agricultural Research (ICAR) and University Grant Commission (UGC) Government of India, for supporting the study in terms of funds and facilities.
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