Ascites in Frogs

Ascites in Frogs
By Dr. Pitcha Phumjampa (Dr. Bai Mon) and Assoc. Prof.

Dr. Sompoch Weerakun (Professor Kaew)

Ascites (fluid accumulation in the abdomen) in bullfrog species, such as the Argentine bullfrog, and in various ornamental frogs, is commonly observed. The accumulation of fluid begins with a small amount, but can lead to the visibility of air-filled organs like the lungs on an X-ray. In the early stages of fluid accumulation, it may be overlooked by the examiner and mistaken for fat deposits. Although the X-ray of the frog should provide sufficient details of the organs, early stages may be misinterpreted.

In chronic cases, fluid accumulation becomes more evident, resulting in a completely white image, which contrasts more clearly with the lungs. This resembles pleural effusion seen in mammals, though fluid accumulates throughout the entire coelomic cavity (body cavity).

The most likely cause of ascites in frogs in Thailand is a low protein level in their diet. Most diets consist of fish food or frog food, or food with a high proportion of plant-based ingredients, which may have low protein content. Many frogs suffer from metabolic bone diseases, likely caused by nutritional deficiencies and poor management. In a study of bullfrogs with ascites that were fed a high-protein diet (40% protein), it was found that the fluid cultured from the ascitic fluid did not contain any bacterial infection, indicating that ascites in this group was not caused by a bacterial infection. Further studies also showed liver and kidney diseases that aligned with inflammation in these organs. All cases showed chronic conditions with fluid retention in multiple organs, including the liver, kidneys, lungs, and heart. The kidneys appeared darker in color, and the liver showed both dark and pale areas compared to normal liver tissue, with these two organs being the most noticeably affected.

Granulomas were observed in the kidneys, with eosinophilic hyaline infiltrations. The kidneys showed hypoplasia and an expansion of Bowman's space. Dystrophic calcification was found in the parenchymal layer, and areas of hemorrhage around blood vessels were observed. Fibrinoid deposits and pigment granulomas were also present in tubular cells (Filho et al., 2019). In the liver, melanomacrophages were seen in the parenchyma, along with inflammation sites containing mono-lymphocytes, which caused liver cell damage and death. The large number of macrophages in the liver suggests significant destruction of the parenchyma, possibly due to environmental toxins. Granulomas found in multiple organs are often associated with Mycobacterium infections. Routine bacterial culture may not detect this pathogen, which warrants caution in misdiagnosing, as Mycobacterium is commonly found in aquatic animals. Thus, the possibility of this infection should still be considered.

It was also suggested that the chronic nature of this condition could lead to recurring symptoms, and that liver issues might stem from protein-mineral deficiency. It is believed that low-quality food contributes to liver and kidney damage.

Reports have supported the idea that ascites in several cases is caused by protein and mineral deficiencies, leading to degeneration of liver cells (Cecil, 2006). Low-quality food or plant-based ingredients in the diet, despite frogs being carnivorous animals that require high protein intake, can lead to liver dysfunction (Hipolito, 2004; Vannevel, 2006; Seixas Filho et al., 2008, 2010).

The treatment approach is challenging because chronic ascites can result from various causes. The first step should be to evaluate the diet, followed by differentiation of infectious conditions through bacterial culture or PCR testing. Non-infectious causes, as mentioned earlier, should also be assessed, and supportive care should be provided to slow the progression of organ damage.