Just in Time for Thanksgiving: Fowl Cholera

By Jonathon Marioneaux

Let’s finish the series on birds this week with one of the most ubiquitous diseases that affect our distinguished guests on Thanksgiving: fowl cholera.  First, we will look at what cholera is including a general overview of its structure and transmission.  We will then explore the clinical symptoms and if there are any treatments to protect birds.  We will then conclude with a farewell to our series on turkeys and introduce our next topic: plant diseases.

Pasteurella multocia was first characterized in the 1880’s by Louis Pasture as the causative agent of fowl cholera.  It was soon recognized that P. multocia had three distinct subspecies multocida, spetica, and gallicida with gallicida being the most common.  All birds are susceptible to cholera to varying degrees with waterfowl and turkeys being more susceptible than chickens or other land birds.  P. multocia is a gram negative coccobacillus that stains with Wright stain on its variable carbohydrate surface.  It resists phagocytosis by macrophages and neutrophils with a lipopolysaccraccharide capsule covering a highly hydrated polysaccharides cell wall (Chung et al. 2001). No single virulence toxin has been shown to cause virulence, however several proteins are suspected: capsule endotoxin, outer membrane proteins, iron binding systems, heat shock proteins, neuraminidase, antibody cleaving enzymes, and P. multocida exotoxin (Chung et al. 2001).  The bacterium is highly motile in water and can transfer hosts without direct contact when in close proximity.

The disease is spread primarily by feces or nasal fluids, however it can also be spread by contaminated water, food, bedding, humans (shoes and clothes), and other animals, primarily pigs.  P. multocia causes explosive greenish diarrhea and nasal and oral discharges that can directly infect new hosts (Overview, 2014).  Infected birds can also pass the bacterium by touching feed with open lesions, distended wattles and combs, and contaminated feathers.  Introducing new or wild birds that have not been properly quarantined can introduce the infection to otherwise healthy flocks.  Reservoirs such as pigs and dogs are known to harbor the pathogen as asymptomatic carriers and can spread it to flocks if allowed to mingle with the birds.  Transmission is also a problem with humans when moving between flocks because contaminated feces can stick to boots or other clothing and then be picked up by birds through open cuts or mucus membranes.  Finally, transmission is very common with asymptomatic carriers in large flocks such as factory farms and is less of a problem in free range birds because the bacterium is susceptible to heat and drying out (PM-Onveax,).

Cholera is known for its high morbidity and sudden mortality in large numbers of birds.  Symptoms of infection anorexia, ruffled feathers, oral and nasal discharge, and depression, so careful observation of animals should be carried out routinely.  Other signs might include fibrous contents in distended waddles and excessive red blood cells in livers in post mortem autopsies.  Treatments with penicillin and proactive bacteria can be effective against P. multocia, however caution should be used because antibiotic resistance has been shown to occur rapidly (Fowl cholera, 2014).  A new cholera vaccine is being developed using a highly pathogenic attenuated isolate while an established vaccine uses a mild variant administered under the wing (Hertman et al. 1979).

In conclusion, turkeys are susceptible to bacterial infections primarily by fecal-oral transfer and open lesions.  The most common treatment is oral penicillin or live attenuated vaccination injected under the wing.  With Thanksgiving tomorrow, remember to take extra care of our feathered friends—they can get sick just like us, but with the proper treatment we can take care of them.

This concludes our session on diseases that affect birds; birds are all around us and their diseases deserve to be studied more in-depth because they can teach us a lot about diseases that affect mammals.

Our next series will cover fungal plant diseases in preparation for the winter festivities.


Image Credit: Plainville Farms

Chung, J. (2001, January 1). Role of Capsule in the Pathogenesis of Fowl Cholera Caused by Pasteurella multocida Serogroup A. Retrieved November 22, 2014.

FOWL CHOLERA – Diseases of Poultry. (n.d.). Retrieved November 22, 2014, from http://www.thepoultrysite.com/publications/6/diseases-of-poultry/181/fowl-cholera

Hertman, I., Markenson, J., Michael, A., & Geier, E. (1979). Attenuated Live Fowl Cholera Vaccine I. Development of Vaccine Strain M3G of Pasteurella multocida. Avian Diseases, 24(4), 863-863. Retrieved November 22, 2014.

PM-ONEVAX-C®. (n.d.). Retrieved November 22, 2014, from http://www.merck-animal-health-usa.com/products/130_163369/productdetails_130_163757.aspx

Overview of Fowl Cholera. (n.d.). Retrieved November 22, 2014, from http://www.merckmanuals.com/vet/poultry/fowl_cholera/overview_of_fowl_cholera.html

Turkey Brooder Pneumonia

By Jonathon Marioneaux

This week we continue our series on bird diseases by diving into a fungal bird disease: Aspergillus fumigatus. We will begin by characterizing the physical and genetic qualities of Aspergillus fumigatus and move into a more detailed analysis of how it is spread. Finally we will wrap up by discussing what precautions you can take to keep our favorite holiday bird safe and healthy for the days to come.

Aspergillus fumigatus is a type of fungus that is commonly found in decaying matter and produces spores from the conidiophores during asexual reproduction that are 2-3 microns in size. Its optimal growth range is 37-50 degrees Celsius which is critical for the carbon and nitrogen cycle for breaking down plant and animal matter. It has a filamentous structure under the microscope and its fruiting bodies appear grey during spore release. A study in Nature found 29.4 million base pairs and 5,000 noncoding regions in its genome (Galagan et al., 2010).

A. fumigatus is an opportunistic pathogen that typically attacks immunocompromised individuals, such as those suffering from previous infections, or the very young. The most typical route of infection is pulmonary where the spores germinate in the warm moist areas of the lungs. The fungi evade immune systems attack through macrophages and lactoferrin (iron scavenger molecule) by overwhelming macrophages and lactoferrin production (Ben-Ami et. al., 2005). After successful germination, the fungi penetrate the pulmonary cell walls and in severe cases spread in the blood system for nutrient acquisition. The nutrients include iron, nitrogen, polypeptides, and byproducts, including gliotoxin, that suppress neutrophil activation through superoxide and apoptosis (Ben-Ami et. al., 2005).

In birds, A. fumigatus is spread principally through contaminated feed products or in unsanitary bedding conditions, however, it has been documented that spores can come through improperly cleaned air vents. Air sampling techniques have found seasonal variation among the types of Aspergillus with variations being significantly higher in the winter than the summer (Ben-Ami et. al., 2005). This may be a result of more spore production in drier conditions—there is an inverse relationship between humidity and spore production. Additionally, poults can be exposed to asymptomatic adult carriers and contract it through mechanical interaction. It typically attacks poults 5 days to 8 weeks of age, however, it has been found in birds with underlying genetic or other disease related conditions. Because the fungus mainly attacks the lungs, symptoms can include heavy or rapid breathing and yellow or grey nodular lesions in the respiratory tract, especially lungs and air sacs.

Currently there are no vaccinations or cost effective cure for A. fumigatus infections, therefore once an infection has been identified the bird must be isolated and culled. Vaccine trials have shown no immunity and in some cases a second exposure has proven fatal. The best protection against A. fumigatus infection is delivered through the preparation of clean bedding, food, and air and the prompt culling of infected animals (Ben-Ami et. al., 2005). In addition, increasing the humidity levels and a light spraying of germicide when the poluts are of sufficient size will also keep the risk of contracting the spores lower (Larson et al., 2007).

In summary, there is a lot of work that goes into creating healthy turkeys but with some simple steps and proactive work flocks will not be overrun by pathogenic A. fumigatus. The fungus is very necessary in the carbon and nitrogen cycle and only causes opportunistic disease in immunocompromised birds. So, enjoy your holiday turkey and next week we will continue our series and investigate more illnesses that plague our avian friends.


Image Credit: Champoeg Farm

Ben-Ami, R., Lewis, R. E. and Kontoyiannis, D. P. (2010), Enemy of the (immunosuppressed) state: an update on the pathogenesis of Aspergillus fumigatus infection. British Journal of Haematology, 150: 406–417. doi: 10.1111/j.1365-2141.2010.08283.x

Galagan, J. (2005, October 5). Sequencing of Aspergillus nidulans and comparative analysis with A. fumigatus and A. oryzae. Retrieved November 16, 2014, from http://www.nature.com/nature/journal/v438/n7071/full/nature04341.html

Larson, C., Beranger, J., Bender, M., & Schrider, D. (2007). Common Diseases and Ailments of Turkeys and Their Management. In How to Raise Heritage Turkeys on Pasture (pp. 35-52). American Livestock Breeds Conservancy.