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Paratyphoid Infection in Poultry

C. A. W. JACKSON, Veterinary Research Station, Glenfield

Paratyphoid is due to infection with Salmonella serotypes other than S. pullorum and S. gallinarium. It is characterised by mortalities from day-old to approximately three weeks of age with few autopsy findings except for cheesy caecal plugs and enlarged livers with a few haemorrhages present. The disease in adults is usually symptomless although a high percentage of birds may remain intestinal carriers after an outbreak. A large number of serotypes have been isolated from poultry, however the majority of outbreaks have been caused by a few serotypes, especially S. typhimurium, with particular serotypes predominating in certain countries. This was the case with S. thompson infection in the United Kingdom and S. heidleberg, S. infantis and S. typhimurium in the United States. The serotypes isolated to the end of 1968 from poultry in Australia are listed in Table 1. S. typhimurium is the most commonly isolated serotype in Australia followed by S. anatum and S. derby. S. derby is reported to be frequently isolated in Queensland. S. typhimurium is by far the most common serotype isolated from poultry in N.S.W.

A substantial increase in isolations of S. typhimurium has been reported in N.S.W. since 1967. From January, 1967, there have been 58 outbreaks of Paratyphoid reported in chickens and eight (8) in turkeys. This compared to only five (5) outbreaks during the period 1962-1967.

The disease has become increasingly important in most countries, particularly because of the danger to human health and because of the difficulties associated with eradication of the disease from breeding flocks and depressing effects on hatchability and egg production.

TRANSMISSION

The organisms are transmitted by ingestion of contaminated material and via the egg. Direct ovarian transmission occurs rarely in fowls, occasionally in turkeys and more commonly in ducks. Egg transmission in fowls mainly occurs through faecal contamination of the shell and a subsequent penetration of the shell. Penetration of the shell varies with the virulence of the serotype involved and usually occurs during the first week of incubation. The cycle of infection is then the same as Pullorum Disease with a small percentage of infected chickens hatching and spreading infection by inhalation or ingestion of infected material to clean chickens in the hatcher or brooder. As in Pullorum Disease, mechanical spread of infection can occur from contaminated boots, brooms, trucks, equipment and free flying birds. Additional sources include contaminated feed, especially meat meals, and rodents, domestic animals and man which may harbour a latent infection.

Faeces appear to be the most common source of infection with intestinal carriers harbouring infection up to 16 months after initial infection. The organisms have been found to survive for up to six months in faeces and up to 12 months on egg shells under certain conditions.

SYMPTOMS

Chickens and poults are often found dead or they may appear depressed, huddled, ruffled and show diarrhoea. In ducklings a fairly constant symptom is that immediately after drinking they "keel" over backwards and die. Adults rarely show symptoms except under stressful situations. Mortality rates up to 25 per cent have been recorded in recent outbreaks in poults in N.S.W. Losses in chickens are usually less than 5 per cent.

POST-MORTEM FINDINGS

Commonly "cheesy" plugs are found in the caeca. Less commonly the liver is swollen and mottled with haemorrhagic streaks (cedaring), fibrinous pericarditis, and occasional necrotic foci in the liver. Still less frequently there may be pus in the anterior chamber of the eye and excess synovial fluid in the joints. Adults may show necrotic ulcers in the intestines and distortion of the ovules particularly in ducks and turkeys.

DIAGNOSIS

1. Presumptive: Chickens or poults showing the above symptoms with the presence of cheesy caecal plugs. A positive reaction with Salmonella pullorum whole blood antigen is added evidence.

2. Definite: Isolation of pathogenic Salmonella serotypes especially S. typhimurium by bacteriological examination. It is recommended that at least six birds be cultured. Isolation techniques should include direct culture from any lesion to the extent of smearing the cut surface of a lesion directly on to a plate of artificial media. Cloacal swabs are of value in detecting intestinal carriers. A variety of suitable artificial media are available including Brilliant Green Agar, MacConkey Agar and S.S. Agar. Where lesions are of a more chronic nature, it is wise to carry out preliminary culture in enrichment broth. Pooled tissue including, heart, liver, lungs, spleen, pancreas and intestines are incubated in Selenite or Tetrathionate broth for 18-24 hours. A loopful of broth is then streaked on one or more of the selective media above and incubated and examined every 24 hours. It is unwise to discard Brilliant Green plates as negative under seven days. Suspicious colonies are subcultured for purity checks and either an indicator medium such as Kohns Two Tube Medium (Oxoid) or Triple Sugar Iron Agar (Difco) is inoculated and slide agglutination tests are conducted with specific somatic and flagella Salmonella Agglutinating antisera. Standard cultural methods for Salmonella have been developed overseas and are recommended.

TREATMENT

A number of drugs are available which will reduce the mortality in acute outbreaks and in preventing the spread of the disease. All drugs have, however, the disadvantage that they do not eliminate the carrier state. Drugs currently in use include Neftin Supplement (R) at 4 lb./ton for ten days (the dose for ducks should not exceed 1 lb./ton), Chloramphenicol (R) at 25 mg./bird for five days and Aureomycin (R) at 200 mg./gallon for five days. Additional drugs which are available on prescription and have proved successful are combinations of sulpha drugs and electrolytes.

Preventative medication programmes have been used from day-old when an outbreak is likely with such drugs as Neftin Supplement (R) at 1lb./ton from day-old, Gallimycin (R) at 50 mg./bird for five days in the drinking water, Aureomycin (R) at 200 m./gallon for five days, Terramycin (R) at 400 mg./gallon for five days or Chloramphenicol at 2.5 mg./bird for five days. (R)-Denotes registered trade mark.

CONTROL AND ERADICATION

Control and eradication of this disease has been limited to individual flocks in most countries although the U.S.A. has included a control programme for S. typhimurium infections in turkeys under the National Poultry Improvement Plan. A number of states in the U.S.A. have voluntary S. typhimurium control programmes principally in turkeys.

One of the limiting factors in control is the lack of adequate methods to detect carriers in infected flocks. It has been found by a number of workers and confirmed with observations on a breeding flock in N.S.W. that intestinal carriers may reveal no serological response to the agglutination test, and titres of birds that do react, may fluctuate widely. The tube agglutination test has however been applied successfully in the U.S.A. in eradication when accompanied by complete disposal of infected flocks and restocking from a clean source. The difficulties associated with the application of the tube agglutination test on a large scale have prompted investigations into the value of a rapid whole blood agglutination test (RWBT). Results to date have indicated that the RWBT is met with the same limitations as the tube test due to the variable antibody response by infected birds.

Testing programmes for paratyphoids are further complicated by the large number of antigenic types of the organism. An indirect haemagglutination test has been described which should be of value in that it is possible to sensitise red cells to a number of different Salmonella serotypes and thus detect multiple infections in a flock.

The difficulty in eradicating this disease is indicated by the need to resort to complete depopulation in many cases. Depopulation has been found to be necessary particularly when the organisms have become isolated in the vital organs. The disease has, however, been eradicated successfully from some flocks in the U.S.A. by the application of a number of control measures concurrently. Goetz (1962) described the California eradication programme for turkeys which included the bacteriological sampling of all poultry mortalities to 21 days of age and routine bacteriological sampling of dead-in-shell embryos to support agglutination testing of breeding stock in detecting infected flocks. At a recent conference at the University of California a study committee on paratyphoid considered that the above methods to detect and eliminate infection should be supported by additional tests such as microbiologic examination of rectal swabs and faeces, fluff in hatcheries, cull chicks and birds at processing plants. The use of the above measures where depopulation is impractical together with thorough hatchery and flock sanitation should allow eradication in valuable breeding flocks. Hatchery and flock sanitation must be emphasised as faecal contamination of hatching eggs by chronic carriers and from an infected environment are the means by which infection is generally introduced. Williams (1965) has outlined the practical requirements of control and eradication in some detail. Collection of eggs at frequent intervals, early fumigation and storage in a cool place for as short a time as possible, is very important. Thorough fumigation procedures should be carried out at the hatchery and contamination from infected personnel and rodents should be avoided. Flock sanitation is of equal importance. Observations in N.S.W. have indicated that rodents can be a dangerous source of reinfection and that a rodent eradication campaign should be instituted to the extent of supplying concrete floors to all pens. An investigation in the United Kingdom found that 2.88 per cent of wild birds yielded Salmonella on autopsy, indicating the importance of wild birds as a source of reinfection. One of the difficult sources of infection for the farmer to eliminate is contaminated finished feed. The responsibility must lie with the feed manufacturer to ensure appropriate manufacturing processes such as pelleting of finished feed and the application of procedures to prevent contamination of finished feed products.

At present the control and eradication of Paratyphoid is in the hands of the owners of individual flocks. The introduction of official control measures on a state basis will depend upon the danger to the rest of the industry and to human health. It is considered that the recent increase in outbreaks in chickens and turkeys requires definite action by authorities at this stage, such as (1) Surveillance of all Salmonella isolations by making the disease notifiable; (2) Study of methods for the decontamination of feedstuffs; (3) Investigation of improved serological and other procedures to detect infected flocks; (4) Development of standardised procedures for the fumigation of eggs and general hatchery and flock hygiene, and (5) the development of an overall control programme for individual flocks similar to that for Pullorum Disease.

Goetz, M. E. (1962). Av. Dis. 6, 93

Williams, J. E. (1965) in Biester, H. E., and Schwarte, L. H., "Diseases of Poultry", 5th Ed. Iowa State Univ. Press. Iowa, p. 260

TABLE 1 Salmonella Serotypes isolated from Poultry in Australia

Antigenic Group	Chicken	Turkey	Duck
B	S. bredeney
	S. chester
	S. san diego
	S. derby		S. derby
	S. saint-paul
	S. typhimurium	S. typhimurium	S. typhimurium
C1	S. bareilly
	S. braenderup
	S. cholerae-suis
	S. oranienburg
	S. oslo
	S. potsdam
	S. singapore	S. singapore
C2	S. bonariensis
	S. bovis-morbificans		S. bovis-morbificans
	S. glostrup
	S. kottbus
	S. meunchen
	S. newport
D	S. pullorum	S. pullorum
	S. gallinarium	S. gallinarium
E	S. anatum		S. anatum
	S. give	S. give	S. give
	S. lexington
	S. london		S. london
	S. meleagridis		S. meleagridis
	S. orion	S. orion	S. vegle
	S. zanzibar		S. zanzibar
E2	S. cambridge
	S. new-brunswick
	S. newington	S. newington
	S. taksony
C2	S. worthington
I	S. salford
O	S. adelaide
Q	S. champaign
S			S. waycross