Toxic hepatoenteritis in poultry
Some SH2-producing Enterobacteriae are responsible for the appearance of infectious toxic hepatoenteritis in birds, which produce growth inequality and retardation, as well as bad conversion and less productivity. The control of hydrogen sulphide-producing Enterobacteriae (Proteus spp., E.coli spp., Pseudomonas spp., Salmonella spp.) is basic from a sanitary point of view and, consequently, from the point of view of productivity.
The right diagnostic of the disease and the control once the first symptoms appear is the only way to avoid loss of productivity and, consequently, economic losses. The transmission in birds is vertical, based on epidemiologic observations and the identification of hydrogen sulphide-producing Enterobacteriae in breeders’ liver and ovaries.
Most breeder batches present no disease signs, or they are very slight. The first symptom of the infection usually appears in their offspring. Therefore, the identification of the disease in breeders must be carried out as soon as possible.
The differential diagnostic is basically effectuated by ruling out mycotoxicosis, and identifying bacteria that causes infectious toxic hepatoenteritis. The identification of the bacteria will allow the application of the right treatment, instead of a symptomatic treatment which disguises the etiologic agent. The specific treatment against the identified etiologic agent will avoid the decrease of productive efficacy.
The control of all the production links, basically focused on breeders, through the periodic microbiologic analysis and the elimination of the seropositive specimens will improve productivity and health quality of the avian products.
Diagnosis of toxic hepatoenteritis
1. Symptomatology in breeders and broilers exemplified in images:
2. Isolation and identification of bacteria causing the infection
a. Sample taking
b. Enrichment medium
• Rappaport Vassiliadis semisolid medium
High selectivity medium for Salmonella. Optimum performance at incubation temperature of 43ºC. Its selectivity is based on the capability of Salmonella spp. to support high osmotic pressures, to reproduce at low pH, to resist malaquite green and the need of just few nutrients.
• Brilliant Green Bile 2% Broth
Enrichment medium for coliform bacteria. Bile inhibits Gram- positive growth while green malaquite inhibits gram- negative growth. Microorganisms that ferment lactose produce gas. This medium allows coliform and Salmonella to grow.
c. Specific medium
Salmonella and enterobacteriae SH2 producers: SH2 production is an indicator of the presence of thiosulphate and iron, which make a reaction that produces a black-coloured precipitate.
Escherichia coli: The produced acid due to fermentation at low medium pH makes it to change from red (basic) to yellow (acid).
• Enteric Agar of Hektoen
Escherichia coli: The acid produced due to fermentation at low medium pH makes it to change from green (basic) to yellow (acid).
E.coli and Salmonella: non lactose-fermenting bacteria, as Salmonella, has a green coloration. In the case of de SH2-producing bacteria, it indicates the presence of thiosulphate and iron, which makes reaction to produce a black-coloured precipitate.
d. Confirmation Culture Medium
- Triple Sugar Iron
This medium is intended to identify different kinds of enterobacteriae based on their biochemical differences in the fermentation of glucose, lactose, sacarose and H2S production.
It is recommended to use it routinely to make an antibiogram in solid medium for the following reasons:
– Good reproducibility batch by batch in sensitivity tests.
– Content in sulphonamides inhibitors, trimethoprim and tetracycline.
– Most pathogenics grow correctly.
– High number of evaluated and contrasted data recommend the use of this culture medium.
f. Bacteria identification
The system API 20 E is successful in the identification of microorganisms from the Enterobacteriaceae family, such as some Gram- negative bacillus.
The gallery includes 20 microtubes with dehydrated culture mediums. Tests are inoculated with a bacterial suspension and, then, microorganism’s metabolism cause colour changes to the medium either in just one moment or later once a reactive is added. After 18-24 hours at 35-37 ºC, colouring needs to be translated by following the interpretation table.