Fowl typhoid can become a multi-bacterial disease in poultry

ATLANTA, Jan 27 – New research from Mississippi State University is helping our understanding of this disease of laying hens.

A severe disease of poultry, particularly brown egg layers, fowl typhoid is caused by Salmonella Gallinarum (SG). Various factors have been identified to predispose birds to the disease, and recent work by Martha Pulido-Landinez of Mississippi State University has identified the presence of a second pathogen, Gallibacterium anatis (GA), in some cases in Latin America. Dr Pulido-Landinez discussed her findings at the International Poultry Scientific Forum, in Atlanta, U.S., an event organized by the Southern Poultry Science Society alongside the International Production and Processing Expo (IPPE).

Previous work has shown a link between outbreaks of SG and poor management of the faeces of earlier flocks.

“There is no magic bullet to control disease. However, working with producers to enhance biosecurity, vaccination programs, manure management, water quality and intestinal health, I am so happy to tell you that we have tell you that we have had success in turning SG-positive farms into SG-negative ones,” Pulino-Landinez said.

During the study, SG was been isolated mainly from the liver, spleen, bone marrow and ovary follicles of sick birds. The researchers then found GA in the trachea, lungs, ovary follicles, and oviduct of some affected hens. GA is a normal inhabitant of the respiratory and reproductive system but it appears to contribute to the occurrence, symptom severity and persistence of SG.

On the 220,000-bird layer flock studied, first symptoms of disease included depression, followed by an increase was seen in mortality.

SG and GA can have major adverse effects on performance. Cumulative mortality to 70 weeks was 16.7 percent in affected flocks when only SG was isolated, rising much higher when both pathogens were present. Typical mortality in healthy flocks is 3.8 percent. Average number of eggs per hen housed were 280.0 for the SG-only flocks and 247.7 with both SG and GA, compared with the typical 306.9 eggs for a healthy flock.

“These kinds of results are very important for the profitability of the flock,” said Pulido-Landinez.

In the poultry houses where both pathogens were found, mortality and egg production drops were more severe than with SG alone. The researchers also found respiratory problems in flocks infected with GA.

Among the common factors on affected farms with both pathogens were chicken houses located within 15 meters of each other – especially when young hens (19-30 weeks of age) were in close proximity to old hens (more than 70 weeks of age) – and the presence of cattle on the farm, which is a common practice in some areas.

Control of the pathogens will be particularly challenging as Pulido-Landinez’s study showed that both pathogens were multi-resistant, and do not share susceptibility to any commonly used antibiotics. As she pointed out, antibiotic treatment of laying hens risks the presence of antimicrobial residues being found in shell eggs.

“Working with producers to enhance biosecurity, vaccination programs, manure management, water quality and intestinal health, I am so happy to tell you that we have tell you that we have had success in turning SG-positive farms into SG-negative ones,” Pulino-Landinez added. “The next step is to develop a vaccine against the GA present.”