Macrorhabdus in Budgerigars by Sharman Hoppes, DVM, ABVP-Avian Pacifi c Veterinary Conference Speaker

Macrorhabdus ornithogaster is an important fungal appetite. Depression, regurgitation, diarrhea and disease in parrots, especially the smaller parrots maldigestion have also been noted. Melena may be (budgerigar, cockatiels and finches). Macrorhabdus seen in end-stage disease and death may occur due ornithogaster is thought to be the etiologic agent of to hemorrhage. Occasionally acute macrorhabdus the “going light” syndrome in budgerigars. “Going disease may be seen in budgerigars, where an light” in budgies is characterized by weight loss, apparently healthy bird suddenly becomes depressed diarrhea, regurgitation and death. Macrorhabdus and dies within 24 hours. has been reported in canaries, finches, cockatiels, lovebirds, chickens, ostriches and occasionally in Differentials include: trichomoniasis, candidiasis, larger parrots. bacterial ventriculitis, heavy metal toxicity, neoplasia and proventricular dilatation disease. Believed initially to be a bacterium, for years it was called megabacteria. Recently it was determined Diagnosis in the live bird can be challenging. M. that Megabacteria was actually a yeast and thus was ornithogaster can be seen in wet mounts of feces renamed Macrorhabdus ornithogaster. or on proventricular scrapings with Grams or romanowsky stains, but shedding is intermittent so Macrorhabdus is a large, gram-positive rod-like it may be difficult to detect. A complete blood count structure measuring approximately 1 to 5 mcm in (CBC) and biochemical profile are typically non- width by 20 to 90 mcm in length. M. ornithogaster specific. Contrast radiographs with barium sulfate stains positively by periodic acid-Schiff and silver may reveal a “sandglass-like” appearance between staining techniques. Electron microscopy has revealed the proventriculus and ventriculus. There is a PCR a three-layered wall with indentations in the inner test available that can be done on feces that is more wall and a translucent outer wall and the presence of sensitive than wet mounts. Definitive diagnosis of M. eukaryotic nuclei within a nuclear membrane. Fungi ornithogaster is most often demonstrated at necropsy. by definition are eukaryotic heterotrophic organisms. Necropsy often reveals an emaciated bird with major Clinical signs are often nonspecific. Progressive lesions at the junction between the proventriculus and weight loss over months is seen in spite of a good ventriculus. Gross lesions include a proventriculitis with ulcers with or without hemorrhage, dilation of the gastric isthmus, thinning of the isthmus wall, and increased mucous secretion.

M. ornithogaster has also been found in clinically healthy birds LEFT: PAS stained image of Megabacteria in the proventriculus of a Cockatiel

RIGHT: Direct smear of macrorhabdus

PAGE 41: Treated birds who are still healthy and well 2 years after treatment with sodium benzoate

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67_3 40-41 | Hoppes.indd 40 5/6/13 11:27 AM and there is some evidence that M. ornithogaster Benzoate is quite bitter so may be a component of the normal gastrointestinal treatment must begin slowly and Sharman Hoppes, flora of budgerigars. Research has revealed that be monitored closely. Overdosage DVM, DAVP (Avian) subclinical infections are present in a large number of can result in neurological signs and budgerigars without any signs of disease. It has also death. Birds that are reproductively been suggested that a bird’s innate susceptibility to active, feeding chicks or in hot infection may be more important than the duration environments tend to drink more, of exposure. The mode of infection is fecal-oral, but sometimes two to three times more there may be genetic factors involved because the water daily than normal. In these prevalence of macrorhabdus is significantly higher in cases the dose must be ¼ to ½ the chicks from M. ornithogaster-positive parents than recommended treatment dose to be from M. ornithogaster-negative parents, even when safe. raise by M. ornithogaster-negative parents. Begin with ¼ teaspoon of 100% Dr. Hoppes is an Treatment has been challenging. Historically the sodium benzoate powder in one only effective treatments have been amphotericin B liter of water. Monitor water intake associate professor and Nystatin; polyene macrolide antifungals which for a few days, and if the bird is of Zoological bind to ergosterols in the fungal cell membranes. drinking well increase water intake Medicine at Texas Amphotericin B is most effective in birds if given to ½ teaspoon per liter of water. A&M University’s orally, either in medicated water or by gavage. If drinking normally over the next College of Veterinary Nystatin has been reported to be effective in two days, increase to 1 teaspoon Medicine. She goldfinches. Although amphotericin B has proven per liter and continue treatment to be effective it is quite expensive in a large flock for four to six weeks. Monitor feces graduated from making it often cost prohibitive. directly for organisms or via PCR Oklahoma State every two weeks. University with A new drug regimen which has shown efficacy her DVM degree in against macrorhabdus in budgerigars is Sodium This can be a very effective water 1993 and worked in Benzoate. Proposed by Dr. David Phalen in Australia treatment if the birds are not private practice for as a treatment for macrorhabdus, Sodium Benzoate reproductively active, feeding is a preservative that is used in jams, sodas, and chicks and if the birds are housed ten years. Dr. Hoppes makeups. It is bactericidal and fungicidal, water in moderate temperatures. is the president of soluble and inexpensive. Studies done at the Schubot the Association of Exotic Bird Health Center confirmed that Sodium Avian Veterinarians Benzoate was an effective treatment. Sodium and has served as chair of their rescue and sanctuary committee and as a board member. She is also a member of the Association of Reptile and Amphibian Veterinarians. At PacVet, Dr. Hoppes leads eight sessions on Thursday and Friday, June 20-21, in Avian Medicine and Surgery.

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