Pigeon parathyphoid is an infection that can cause disease in both birds and people. There are many strains that show differing abilities to cause disease. Generally the strains from pigeons are better adapted to pigeons whereas strains from psittacines, budgies and parrots, can cause severe disease in the bird and respiratory disease in people. The infection can be fatal to both. The following is a description of Pigeon Paratyphoid
Table of Contents
Synonyms
Pigeon paratyphus, Pigeon salmonella
Cause
Salmonella typhimurium var Copenhagen, a gram negative motile rod shaped bacterium.
Host
Pigeons – seems to be better adapted to pigeons, Birds, Mammals (including man)
Transmission
Bird to bird through the oral faecal route, from parent to squab through the egg. The bacterium can persist in dust and faeces for several weeks to months. this is further compounded by adult birds that can become chronic carriers shed in infection in their droppings at times of stress e.g. hard races. I would suspect that like many other infections, e.g. pigeon pox, pigeon paramyxovirus, infection is introduced to susceptible birds in the race basket. Following the establishment of infection in the intestine, it can then move from here and be spread by the blood stream to other organs such as lungs, liver, spleen, testis, ovary, brain, muscle, skin and joints. Localisation in the ovary allows spread to the chick via the egg (vertical transmission). some pigeons recover spontaneously whilst other become asymptomatic carriers.
The Salmonella survives inside cells such as macrophages or in small abscesses. carriers are very important sources of infection. Sometimes lesions develop in the absence of bacteria. Typically this is the swelling on the elbow joint but it can also occur in the shoulder joint. This may develop months to years after the salmonella has been eliminated from the loft. The fluid from these swellings contains Salmonella antibodies. Precisely how this occurs is not understood. I have never managed to isolate salmonella from these lesions.
Clinical signs
The signs seen will depend on the site of infection. In adults the infection can be subclinical, show signs of loose droppings, wing or leg, lameness or can result in sudden death. Juvenile birds may show signs of watery green droppings, soiled feet and tail feathers, nervous signs, failure to eat, excessive thirst, rapid weight loss and then die. Eggs may fail to hatch and squabs fail to grow and die within 4 to 5 days of age. Other signs can include runny eyes and discharges from the nose. The infection can affect a small proportion of adult birds over a long time whilst with juveniles it may affect 20% in a few weeks.
In my experience, birds with paratyphoid have been submitted as either sudden death in adults, wing lameness or chronic watery droppings associated with poor racing performance.
Pathology
Gross pathology varies with the acuteness of the disease. In birds with wing or leg lameness the lesions may be restricted to an infectious arthritis. The latter may be quite obvious if associated with the elbow but will require careful dissection if affecting the shoulder joint. However, where death occurs there is little or no food in the crop, a congested carcass, green bile stained discolouration to the gizzard lining, enlargement and congestion of the liver and spleen. The kidneys are enlarged and are browner in colour. Urates maybe present in the ureters. Necrotic foci may or may not be present in the liver.
Diagnosis
Diagnosis requires the isolation of the salmonella from the viscera or faeces. I have found that S.typhimurium is more easily isolated from the liver and intestines than the faeces. Isolation of the bacterium from chronically infected joints has usually been unsuccessful. Identification of chronic carriers can be very difficult and may require monitoring faeces over a prolonged period whilst performing post mortem examinations on any birds that may die or are culled. Diagnosis will be more difficult in vaccinated birds and and those receiving routine antibiotic treatments. Blood tests may identify those birds that have had a blood borne infection but they generally miss chronically affected or asymptomatic carriers.
Differential diagnoses
Streptococcosis, adenovirus infection, hexamitiasis, ascaridiasis, capillariasis, pigeon parmayxovirus.
Treatment
When infection is identified in the loft, the flock should be treated with the most suitable antibiotic determined by culture and sensitivity tests. My treatment of choice is Enrofloxacin but current experience shows some resistance so checking the sensitivity pattern is vital.
Prevention
A multi-pronged approach is required to eliminate infection from or prevent infection of your flock. Infected flocks should be firstly treated with antibiotics. Routine annual antibiotic treatments , in my view, will only eventually lead to disappointment as the problem becomes worse.
Then all birds should be vaccinated with either a live or dead Paratyphoid vaccine. This vaccination will need to be repeated annually.
Strict hygiene precautions should be put in place to minimise the spread of infection between sections and lofts. This will mean regular cleaning of drinkers and feeders, the use of disinfectant loft powders, aerosol fogging of disinfectants and drinking water sanitisers. As soon as possible the loft should be emptied of birds and completely cleaned down with suitable cleaners and disinfectants.
Identifying potentially infected birds or parents and culling them is also important. I do not believe that culling all birds in the loft, removing the old loft and starting afresh is a practical way forward. Whilst replacing an old loft with new will be beneficial. You will still most likely be erecting it near where the old loft was. Infection can persist in the soil or in the resident rodent population, recontamination is consequently quite likely. Similarly, it would be virtually impossible to guarantee that any newly purchased stock would indeed be free of infection.
Paratyphoid can be transmitted to the fancier. It is a zoonosis – an infection that can spread from animals to man. The fact that this does not seem to happen is either a reflection of the fact that this organism is better adapted to pigeons than man or that most fanciers develop an immunity to infection or both. However, the young and elderly will be more susceptible.
Ensure that you keep loft shoes and overalls out of your house, especially the kitchen. Make sure you wash your hands before and after handling your birds. Regular use of a hand sanitiser whilst you are going from section to section or loft to loft would also be useful. This is more important for smokers than none smokers. The former may handle birds, scrape clean rings to check the number and then light up; very quickly transferring specks of pigeon droppings from feet to lips.
Occasionally a pigeon will die within 24 hours of being vaccinated whilst others can develop swellings (nodules) at the injection site 7 to 10 days after vaccination. It may be necessary to surgically remove these . Regular monitoring of droppings at least monthly will be required to establish freedom from salmonella infection. Whilst it may be possible to improve race performances within the year. Expect to take several years to remove infection from your loft.
Salmonella typhimurium is the 19th commonest diagnosis made by my local AHVLA labs. Details of species affected, clinical signs and post mortem lesions observed can be found by clicking here.
