2007-2011 Summary of analyses of results of laboratory tests for salmonella and salmonellosis in poultry and feed in Bulgaria

The problem of salmonella in poultry and salmonellosis in our country became a rather topical one with the latest developments in industrial poultry farming.  Against the expectations, it turned out that the intensive poultry farming and the relevant intensive methods of farming and feeding do foster development and spread of pathogenic micro-organisms, especially salmonellas.  Gyurov et al. (2006 ) outline that the dominant types of salmonella in poultry are S. enteritidis, S. gallinarum and S. typhimurium are present in 80% of all the isolates, thus justifying the necessity of regular monitoring of such targeting.  Everywhere in diagnostic units countrywide, there is well identified trend of more and more decreasing number of incoming biological samples for pathological examination and microbiological testing and it requires appropriate efforts to be overcome.
This study place the focus of analyses on microbiological tests performed on diagnostic materials in laboratories of National Diagnostic & Research Veterinary Medical Institute (NDRVMI) and in others in the country, and also on the trials carried out to achieve a more comprehensive monitoring of flocks of identified salmonella infections.  Furthermore, it explores the isolates of the Salmonella strains and summarises the results generated by all the National Programmes for Control of Salmonellosis in Poultry (NPCSP), which cover flocks of breeding stock, laying hens, broilers and turkeys.  Subject to analyses are also the methods applied for testing for salmonella and salmonellosis in poultry-breeding and the results collected from testing for salmonella bacteria in feed.
Laboratory data on poultry cover the five-year period since 2007 till 2011 and are generated by the tests performed in the laboratory named ‘Bacterial Diseases in Poultry’ with the NDRVMI, where a total of 11269 samples have been tested as taken from fallen poultry and their environment in accordance with the requirements laid down in the NPCSP.  This total is broken by years, as follows:
• Year 2007:  636 samples tested for S. enteritidis in day-old and six-day broiler chickens (the 2 positive ones were taken from two flocks of no link between each other).  Furthermore, under additional programme there were 3 cases (1+1+1) of three different salmonella species (S. manchester, S. chester and S. typhimurium) found in one poultry farm of broilers, and other two other isolates of Salmonella gr. C were isolated from samples of laying hens of two flocks.
• Year 2008:   There were 2233 samples taken under the surveillance provided for in the Programme for detection of Campylobacter spp. and Salmonella spp., all being also tested (as all others subject to this report) in the above mentioned laboratory.  These samples yielded 86 isolates of Salmonella spp. (ref. the NPCS in broilers for 2008);
• Year 2009:  There were 1970 samples tested to yield (in March) 2 cases of Salmonellas of gr. OC in broiler chickens and a total of 10 isolates;
• Year 2010:  The number of samples tested was 3124 to yield 7 isolates, these including 2 cases of S. typhimurium in fallen herons in January, 2 cases of S. gallinarium (samples taken in backyards) and 1 isolate of Salmonellas of gr. OC of egg-shell samples of broiler chickens;
• Year 2011:  a total of 3306 samples tested to have isolates of Salmonellas in laying hens, all being delivered under the self-control requirements applicable to poultry farms.  The yield was of only isolate of Salmonella gr. OC.
Briefly, there were 11269 samples tested during the whole aforementioned period to yield isolate(s) of S. gallinarum, S. enteritidis, S. typhimurium, S. manchester, S. chester and Salmonella gr. OC.
The NDRVMI Sector named ‘Bacteriology and bacterial diseases in animals, compound feed and raw materials therefor’ have testing activities in feed to detect Salmonella spp. therein.  The summary here is as follows:
o 2007 – 242 feed samples of two cases of salmonella isolation (one of S. munchen in compound feed for pigs and one of S. ????? in food for home pets);
o 2008 - 206 feed samples tested to yield one case of isolation of Salmonella OE in compound feed for poultry;
o 2009 - 204 feed samples tested and not a single Salmonella isolate;
o 2010 - 148 feed samples tested and not case of S. isolate yielded;
o 2011 - 296 feed samples tested to yield one case of S. isolate (S. hadar).
The brief summary for the whole period is a total of 1094 feed samples tested to yield a total of 4 S. isolates.
In Bulgaria, official control of Salmonella spp. in breeding flocks, laying hens, broilers (Gallus gallus) and turkey is completely encompassed within respective National Plans for Control of Salmonellas (NPCS) broken in respective industrial categories of poultry.
The NPCS in breeding flocks has delivered the following laboratory results:
Ø Year 2008:  A total of 85 breeding flocks subject to respective NPCS, the number of poultry therein, being 997,101.  A total of total of 1168 samples tested as faecal ones and such taken from hatcheries (egg-shells).  No S+ result confirmed;
Ø Year 2009:  The number of flocks under controls was 143 of 1,205,575 poultry and 452 tests performed under these official controls. Five (5) flocks were proven as S+ for the year, as follows: one flock of S. infantis, one of S. bareilly, two flocks of S. senftenberg and one of S. agona.  This makes the percentage of the S+ flocks compared to all flocks included in the programme to be 3,49%;
Ø Year 2010:  The official samples taken from breeding flocks were 368, all these being taken from 151 flocks in 35 farms and a total of 1,569,702 poultry.  The total number of tests performed was 2302 (including the samples taken under the self-control plans of poultry farmers).  The overall results were:  3 flocks found positive for S. infantis, 2 flocks positive for S. hadar, 1 flock positive for S. covalis, 1 flock positive for S. glostrup and 1 flock positive for S. Seftenberg.  This makes 5,3% of positive of all the flocks tested.
Ø Year 2011:  the official controls in breeding flocks involved 253 samples taken from 127 flocks (of 37 farms) encompassing 1,319794 poultry  The samples tested under the farmers’ self-control were 2247.  The output was 4 positive flocks for Salmonella spp. (i.e. 3,15%), one flock being positive for S. typhimurium, 1 flock positive for S. agona and 2 flocks positive for S. livingstone.  It should be outlined here, that the case of S. typhimurium (of sero-group OB) has given also reaction for concomitant infection of S. derby throughout the process of isolate confirmation.
The 2011 percentage of positive animals is 0,55% – the prevalence of sero-types included in the programme.  There was one flock of 7230 breeding poultry which was positive for S. typhimurium, which is rather good one, if compared with the data of previous years, in which the percentage of positive poultry (i.e. the spread/prevalence) was substantially higher.

The NPCS in laying hens sector has delivered the following laboratory results:
ü Year 2008:  A total of 115 farms of laying hens (yielding table eggs), involving 228 flocks of 3,400,784 layers.  A total of 222 flocks have proven to be negative (-) for S. typhimurium and S. enteritidis, while 2 flocks (of 6100 layers) were proven as positive for S. enteritidis.
ü Year 2009:  A total of 246 flocks have been involved within the NPCS in laying hens.  There were 244 flocks proven negative for S. typhimurium and S. enteritidis, while 2 flocks (of 2303 layers) were proven as positive for S. enteritidis.  Four other flocks were positive of other Salmonella types, i.e. one flock was positive for S. abovy, one flock for S. Corvallis, one flock for S. Agona and 1 flock for S. virchov.  Percentage of flocks positive for S. enteritidis was 0,81% (i.e. below 1%).
ü Year 2010:  A total of 275 flocks of 3,173,906 poultry were subjected to sampling and testing under the official Salmonellas detection programme.  Two (2) flocks have been proven to be positive for S. enteritidis and seven (7) for other Salmonella spp., as follows:  6 flocks positive for S. infantis and 1 flock positive for S. parkroyal.  The official samples tested were 460 of 104 farms, while the self-controls samples were 725, all the latter being Salmonellas negative (-).  All this making the year of 1% infection by S. typhimurium and S. enteritidis in the whole sector of laying hens.
ü Year 2011:  A total of 228 laying hens flocks of 2,893,951 poultry were subjected to sampling and testing under the official Salmonellas detection programme (the NMCSP).  Four (4) flocks have been proven to be positive for S. enteritidis and 11 were proven as positive for other Salmonella spp., the latter including 2 positive for S. agona, 1 flock positive for S. hadar, 3 flocks positive for S. kottbus, 4 flocks positive for S. barely and 1 flock positive for S. infantis.  This year official samples tested were 325 (of 104 farms), while the self-controls ones were 715.
The 2011 data show an increase in the percentage (%) of Salmonellas positive (+) cases and higher level of prevalence of the serotypes provided for in the NCPS in this laying hens sector.  Percentage (%) of positive poultry was 1,31% for the targeted Salmonella serotypes demonstrated by 4 flocks (of 37800 poultry) of laying hens positive for S. enteritidis.  This could be compared with the same indicator (prevalence) for 2010 which was then 0,88%.
The NPCS for Salmonella spp. and Campylobacter spp. within the broiler sector has yielded the following laboratory results:
Ø Year 2008:  The number of samples tested was 327 samples taken in 13 broiler fattening farms (Gyurov, B. I. et al. 2011 and in more details Valcheva R et al. 2011).  Here, laboratory results has identified 86 salmonella strains of 16 different serovars that are, as follows: S. infantis – 14; S. enteritidis – 18; S. montevideo – 22; S. virchov – 5; S. menden – 4; S. thompson – 3; S. kottbus – 2;  S. typhimurium -1, S. give -1;  S. concord – 1;  S. newport -1;  S. bonariensis – 1; S. kiss -1;  S. irumu – 1;  S. parkroyal -1 and S. Group C1 (6,7: - :-) – 10.
Ø Year 2009:  A total of 1069 flocks tested for Salmonella spp. under official control represented by 1471 samples tested to cover an array of over 22085874 broiler chickens. Three (3) flocks were positive for S. enteritidis, one for S. virchov, two (2) flocks were positive for S. kottbus and one (1) for S. agona.  The test results give grounds to consider the objective of the programme achieved, without any technical difficulties. The percentage of positive flocks (prevalence) for the whole 2009 was 0,37%, which is well below 1%.
Ø Year 2010:  More than 18,916,348 broilers were covered by official controls by a total of 1094 official samples taken from 1088 flocks of 159 broiler farms.  Only one (1) flock was proven as positive for S. typhimurium, while 14 flocks have demonstrated other serovars of Salmonella spp., but none of them all was S. enteritidis.  These 14 isolates of Salmonella spp. were as follows: 10 flocks of S. infantis; 1 flock of S. newport, 2 flocks of S. tennessee and 1 flock of S. mbandaka.  The tests performed on self controls covered all the 2077 samples taken by broiler farmers, but all were proven as negative for the targeted Salmonella spp.
Ø Year 2011:  Official samples from broiler flocks were 513 taken from 1867 flocks in 171 farms (29,277,987 broilers).  Within this whole year period there have not been any flocks of detected (positive) cases of S. typhimurium or S. enteritidis.  Twelve (12) flocks were positive for other Salmonella serotypes.  These are as follows:  3 flocks were positive for S. infantis, 4 flocks were positive for S. livingstone and 5 flocks were positive for S hadar.  In the year there were also 1865 tests performed on samples taken under the self control of broiler farmers, but these have not yielded any positive (S+) for the targeted Salmonella spp.
There are very few farmers keeping turkeys for fattening, this making the results of this ‘fattening turkey’ sector very brief.  In 2010 there were 8 pooled samples taken and tested as negative, the same being the case of 2011, in which the number of samples tested was four (4).
Usage of vaccines is not prohibited for poultry flocks.  Vaccinations take place in breeding flocks (Gallus gallus) and in flocks of laying hens.  Vaccines (live or inactivated) should and are all involved in the registrar of veterinary medicinal products (VMPs).  Only the vaccine authorised by the only national Competent Authority, i.e. Bulgarian Food Safety Agency (BFSA) may be used in Bulgaria.  Vaccination against Salmonella spp. is targeted at the three main serovars of importance in poultry farming, i.e. farmed poultry are subject to vaccination against S. gallinarum, S. enteritidis and S. typhimurium.
The situation with breeding flocks covered by vaccination during recent years is as follows:  2008 – of 85 flocks (of 1,205,575 poultry) the vaccinated ones were 54 flocks (of 204 000 growing up parents);  2009 – of 143 flocks (of 1,205,575 poultry) the vaccinated ones were 104 (of 747,750 growing up parents) plus 101 flocks (of 565 500 parents);  2010 – of 156 flocks (of 1,569,702 poultry) there were 116 vaccinated flocks (of 936,884 growing up parents) plus 87 flocks (of 373,560 parents);  2011 – of 127 flocks (of 1,319,794 poultry), there were 111 vaccinated flocks (of 1,310,136. parents) and another 77 flocks (of 480,545 growing up parents).
As for the laying hens sector the situation demonstrates progressively increasing number of vaccinated flocks between 2008 and 2011.  The 2011 total gives 1088 flocks (of 130,797,780 layers), of which 283 were the vaccinated flocks (of 4,275,665).
The annual developments and implementation of National Programmes for Control of Salmonella (NPCS) in poultry has proven its disciplining effect on both official controls bodies and the self-control activities applied by poultry farmers.
However, a pending necessity it ensure improvement of sampling performed under the self-control plans of poultry farmers or making it incorporated within official controls plans and actions.
Furthermore, there is a need to conduct well planned observations and tests on the effectiveness