-------------------------------------------------------An update on Megabacteriosis. Megabacteriosis is the disease caused by a fungus, Macrorhabdus ornithogaster. Although known since the seventies we see an increasing incidence of this disease. Very often, stool samples are positive for megabacteriosis. This is not always significant as lots of birds do harbour some megabacteria in their gastrointestinal tract. In my opinion, birds without predisposing factors will not catch clinical important disease from this. Most often, clinical disease is known as birds eating all day long, with undigested seeds in their stools, sometimes regurgitating food. This is the worst-case scenario, as these birds will lose weight till starvation. Even with correct treatment, outcome is bad. Often megabacteria infections of this type are associated with some other underlying associated disease. Less severe infections do result in birds not getting into full condition, as because of the disease nutrients are not well absorbed from the intestinal tract. Males not getting the right breeding condition resulting in clear clutches of eggs. In new born chick mortality is typically seen between day 6 and day 12 of life if they are infected with mega bacteria. They get these mega bacteria from the feeding mother. But what are the predisposing factors for megabacteriosis? - Inbreeding. Inbreeding does result in birds with a weakened immune system making them vulnerable for all kind of infections. - Stress. Stress can be of nutritional origin due to a lack of appropriate feeding. But it can also occur from over population, moving birds and the stress associated with the breeding period. - Food. It has been shown if birds get a formulated diet (pellets) megabacteriosis occurs very often. In one study it was shown birds fed a pelleted diet, 48% of them had megabacteriosis versus 3.5% in birds fed a seed diet. This brings us to some new information coming from dr. Walker from Australia. His study showed our birds, who are in fact granivorous and insectivorous are getting foods which are too soft for them. In this way the stomach loses its muscle strength, something like a loose pouch, making it the perfect place for harbouring megabacteria. - Borna virus infections. These infections are very well known by parrot breeders, who call it proventricular dilatation disease. This disease affects the neural system of the birds. Symptoms are either gastrointestinal, like undigested seeds in the stools or neurological like vertigo, seizures, inability to fly and visual problems. Birds can be asymptomatic, show some gastrointestinal symptoms only, or some neurological symptoms only, making differential diagnosis very hard. In Germany prof. Rubbenstroth showed 40% of canary lofts did show infection with this borna virus. So certainly, an emerging problem! Very often these birds have mega bacteria in their stomach, also because of the dilatation of the stomach making it the perfect place for multiplication. - Antibiotics. Long term use of antibiotics does favour culture of mega bacteria. In this we must emphasize this does concern antibiotics like tylosine, doxycycline, sumfamids like ESB. The exception is Baycox which is not an antibiotic. - Atoxoplasmosis. It has very often been shown on autopsies on birds there is an association between birds being carrier of low grade atoxoplasmosis infection together with megabacteriosis. Probably the atoxoplasmosis weakens the birds, making them vulnerable for megabacteriosis.
Transmission of megabacteriosis is from bird to bird by infected stools, or from the hen to her chick by feeding. Transmission through the eggs has not yet been proven. What can we do? Most important is trying to avoid the predisposing factors. - Avoid inbreeding and if you do so do cull all sick birds rigorously. A supplement containing beta glucans can be of use (Immuno Plus, Top S) - Stress: correct feeding regimen with all necessary nutrients. - Pelleted diet: stick with a seed-based diet. - Bornavirus infections: no flock therapy has been shown to be effective, so culling is the only way. In parrots therapies are there with anti-inflammatory drugs, but we cannot use these on our birds. - Antibiotics: avoid long term usage or blind antibiotic therapies. Baycox being the exception. - Atoxoplasmosis: in my opinion one of the main predisposing factors. During the moult, two times a two-day cure of Baycox is acceptable as atoxoplasmosis cannot be cured. Long term ESB treatment suppress atoxoplasmosis but do favour megabacteriosis. If diagnosis of a clinical infection is made veterinary treatment is needed. - Amphotericin B: Known as Fungizone or Fungillin. Flock treatment by drinking water is as effective as giving it twice a day by mouth. It does not dissolve well in drinking water, but if you put some acid it the water it dissolves much better. One can use citric acid or vitamin C for this. There is some discussion about acidification of drinking water for megabacteriosis. Optimal growth for mega bacteria is seen in acid environment. But the main advantage of acidification is the anti-bacterial effect of this. Very often megabacteriosis is associated with anaerobic bacterial infections in the proventriculus and for this reason vets often associate an antibiotic for the first 5 days of amphotericin treatment, which has to be continued for 21 days at an appropriate dosage. Recently it has been shown the efficacy of amphotericin B can be increased with a factor 80 with the addition of squalene, obtained from deep see shark livers. It is sold as a supplement called “Alkylglycerols”. Nystatin: Also effective for treatment and at this moment we often see vets who associate amphotericin B with nystatin. - Other anti fungals like itraconazole or fluconazole have been tested, sometimes with success but often at correct dosage toxicity and liver damage was seen and lowering the dose made them ineffective. - Sodium benzoate has also been proven effective, but mortality was seen at higher doses because the birds stopped drinking - Hydrogen peroxide: Some have used this with positive results, but even more did not see any effect. - Probiotics: Lactobacillus acidophilus has been used with positive results, but more in a preventative setting. Its effect is due to its acidifying property and even more by competitive exclusion. Compare it with a dining table with 6 mega bacteria eating all the food. If you bring in Lactobacillus acidophilus, 3 out of the 6 mega bacteria will be thrown out. This what we call competitive exclusion. If you go for probiotics be sure to use a good brand. Most of these are freeze dried preparations. The problem with a lot of these is lots of the lactobacilli do not survive because of storage temperature being too high and when being rehydrated a lot of them explode, making them useless. For this reason, all yoghurts and actimels are stored in warehouses in the fridge and stored on a lactose base as nutrient for the lactobacilli. In Germany a good probiotic has been developed for birds. It is called Ac-i-prim which contains Lactobacillus acidophilus and has to be stored at -18°C without any lactose in it.
Text : Dr. Jan Vanderborght - Photos: Frans Begijn ( Click on the photos to enlarge ) Also appeared in 'de Vogelwereld' monthly magazine AOB november 2020 volume 76 No. 844