Actinobacillus suis: Serologic evaluation in technified breeding pigs in Lima department.

Summary

The present study had the purpose to determine the presence of antibodies against Actinobacillus suis in pigs coming fron technified breeding farms of the north, middle and south of Lima department. A total of 474 blood samples of pigs apparently healthy, not vaccined against A. suis, aged 17 to 20 weeks of life, were obtained at the moment of profit. Serologic evaluation was made by agglutination in plate using a specific antigen with A. suis, employing three dilutions (1/40, 1/80 and 1/160) and a constant quantity of antigen (0.03 ml). Serums had been considered positive the ones which agglutinated in all three dilutions. It was noticed the presence of reactors against A. Suis in 142 of the 474 samples, with a prevalence of 30% with a higher frequency of positive serums in south and north areas of Lime.

Key words: swine actinobacillosis, dermatitis – nephropathy swine syndrome, Actinobacillus suis, agglutination in plate.

Introduction

The system of intensive breeding of pigs masses big quantities of animals in reduced areas. On the other hand, the active nacional and International trade, the productive and reproductive demand to genetic types and crossings used, and specialized Business in piglets production or fattening animals, predispose to creation of epidemiologic conditions very favourable to the spreading of microbial agents.

Hay algunos patógenos poco frecuentes que habitualmente no son tomados en cuenta pero que pueden llegar a constituir un serio problema en determinadas explotaciones, como es el caso del Actinobacillus suis, considerado actualmente como un microorganismo emergente, sobre todo en granjas de alto nivel sanitario (Miniats et al., 1989), de allí que su estudio se esta profundizando en los Estados Unidos de América, Canadá y Australia, entre otros países. Some little frequent pathogens are not usually taken into account but that can be a serious problema in certain farms, as the case of Actinobacillus suis, considered al present as an emergent microorganism, specially in high sanitary level farms (Miniats el al.,1989), that’s why its study is getting deep in the United States of America, Canadá and Australia, among other countries.

Swine actinobacillosis in its modern conception has been diagnosed in Europe (Germany, United Kingdom, Italy, France and Spain) and America (Canada, Panamá, El Salvador, Honduras, Venezuela, Ecuador and Argentina), with Actinobacillus suis as causal agent, gram negative and facultative anaerobe bacteria (Sanford, 1998).

Scientific literature indicates that the shoots of septicaemia are more common  in farms with high levels of health and specially during the phase of starting operation (lactation and recent weaning) (Sanford, 1995). Economic losses may be important by effect of their high mortality and morbidity, the same as originated by productive problems because of the deficient gain of weight, bad alimentary conversion, increase in number of days in pigs to slaughter, excessive expense in veterinary assistance and medication (therapeutic treatments and vaccinations), and finally for slaughter removals.

 Disease may appear in septicaemia form in newborn pigs, just weaned and young animals, but it typically affects pigs between 2 days and 4 weeks of life (Sanford el al., 1990). It is an infectious disease subacute or chronicle, contagious by vertical transmission, in which course lymphatic ganglions of lumboaortic chain are infected, depending organic chains and spleen also (Borrell, 1995); causing immunodepression,  and so the increase of other bacterial infections is allowed like Bordetella, Corynebacterium, Salmonella and E.coli. Externally, pigs present injuries similar to swine erysipella derived from vascular or immunity disorders, purple coloration in ears and snout due to cyanosis by pneumonia and endocarditis, tearing and  untidy auricular pavilions  derived from the infection extension to parotid and retrofaringeous lymphatic ganglions, and at last,  over coloured urine.

Clinical diagnosis may be wrong due to consecutive diseases superposition, moreover, in the begining of infection symptomes . It is important to make differences between septicaemia by Actinobacillus suis and other diseases that may present with similar macroscopic  injuries like newborn septicaemia by Escherichia coli. On the other hand, experimented clinics have confused injuries from septicaemia caused by Actinobacillus suis with the ones by Actinobacillus pleuropneumoniae in pigs in the end of growth, the same as injuries caused by Erysipella in adults. For all this, bacteriological culture confirmation is important (Sanford, 1992).

Lungs are frequently a good source to diagnose this disease; however, due to their septicaemia condition, the culture of liver, spleen, lymphatic ganglions and kidney in blood-agar seems to be also helpful (Sanford, 1992). However, as the microorganism has difficulties in laboratory growing, it is necessary to resort serological diagnosis, much faster and reliable.

The purpose of the present research was to identify serologically positive animals to Actinobacillus suis by means of agglutination in plate assay, so as to determine the prevalence of infection in technified breeding in Lima department.

Materials and Methods

Samples.

Between February and July of 2003, 474 samples of blood were collected from pigs aged 17 to 20 weeks, apparently normal, not vaccinated against swine actinobacillosis. Animals came from 10 technified farms of North, Middle and South of Lima, and they should go to sacrifice in the main slaughterhouse.

Blood samples were sent to laboratory and to centrifuge at 3,000 rpm during 5 minutes to obtain serums, which had been kept frozen until analysis. The minimum size of samples to process was determined by using the formula to quantify prevalence (Norman and Streiner, 1990).

Serology

Antibodies detection was done using agglutination in plate with a coloured antigen provided by Dr. Jaime Borrell (Biovet, S.A. Spain). The work was done with 0.08, 0.04 and 0.01 ml of each sample of serum and was mixed with 0.03 ml of antigen to obtain dilutions 1/40, 1/80 and 1/160, respectively. They were considered as negative animals the ones with serums which did not agglutinate or they were seropositive until dilution 1/40, suspicious the positive until  dilution 1/80,  and sick the ones which reacted until dilution 1/160, with the purpose to have a better requiring assay. That way, false positive animals could have been removed, which came from crossing reactions.

Results and Discussion.

In Table 1 it is noticed that 30% (142/474) of serum samples of pigs aged to slaughter (5 months or 17-20 weeks aged), coming from technified breeding farms, they were seropositive to antibodies against Actinobacillus suis.

Highest number of positives was found in the South area, with 32.9% (23/70), followed by North area with 32.7% (88/259) and Middle area with 23% (31/135) (Table 2).

Las pruebas de diagnóstico de laboratorio son herramientas para el diagnóstico clínico (Zeman, 1997). En el presente trabajo, a través de la prueba utilizada se pudo determinar la presencia de anticuerpos contra Actinobacillus suis en cerdos en edad de beneficio. A este respecto, el A. suis puede ser considerado un agente primario cuando ingresa al huésped y predispone la entrada de otros agentes infecciosos por causa de una inmunodepresión. También puede ser considerado oportunista cuando ingresa al huésped junto con otros microorganismos, cuando éste se encuentra en estrés y por consecuencia, sus defensas se encuentran disminuidas.Laboratory diagnosis assays are helpful to clinical diagnosis (Zeman, 1997). In the present work, and through the used assay, presence of antibodies against Actinobacillus suis were determined in pigs aged to be slaughtered. Related to this, A.suis may be considered a primary agent when penetrates into guest and predisposes the entrance of other infectious agents because of immunodepression. It also may be considered an opportunist when it comes into guest joint to other microorganisms, when guest is stressed and so its immunity defense is decreased.

The purpose of the present work was to evaluate animals coming from technified farms. There’s no data in the country to quantify or indicate the presence of Actinobacillus suis in extensive breeding animals; however, the high seropositivity of antibodies against this bacteria that’s been noticed suggests to keep working to determine the prevalence in other areas of national territory.

Table 1. Results of serologic evaluation of reactors to Actinobacillus suis in samples collected in main slaughterhouse from pigs to slaughter.

Table 2. Results in different areas of serologic evaluation of reactors to Actinobacillus suis in samples collected in main slaughterhouse from pigs to slaughter.

 Conclusions

 It was found a prevalence of 30% of seropositive pigs to Actinobacillus suis at dilution 1/60, using agglutination in plate method.

•  The presence of antibodies against Actinobacillus suis in technified farms of Lima department suggests the presence of that bacteria in other departments or areas of the national territory.

Mentioned Literature

1. Borrell, J. 1995. Síndrome Dermatitis Nefropatía porcina. Anales de la Real Academia de Ciencias Veterinarias 2: 1-14
2. Norman, G; D. Streiner. 1990. Bioestadística. Mosby y Doyma Libros. Madrid, España.
3. Miniats, O.P.; M.T. Spinato; S.E. Sanford. 1989. Actinobacillus suis septicemia in mature swine. Two outbreaks resembling erysipelas. Canadian Vet. J. 30: 943-947.
4. Sanford, S.E.; G.K.A. Josephson; A.J. Rehmtulla; A.M.E. Tilker. 1990. Actinobacillus suis infection in pigs in Southwestern Ontario. Canadian Vet. J. 31:634.
5. Sanford, S.E. 1992. Actinobacillus suis. En: Diseases of swine. Leman, A.D.; B. Straw; R.D. Gluck; W.L. Mengeling; S. D’Allaire; D.J. Taylor (eds). P. 633-636. 7^th ed. Iowa State University Press.
6. Sanford, S.E. 1995. Actinobacillus suis: An overview of an emerging disease. Proc. American Assoc. Swine Practitioners 26: 425-428.
7. Snaford, S.E. 1998. Actinobacillus pleuroneumoniae and Actinobacillus suis: an update. Proc. American Assoc. Swine Practitioners 29: 357-360.
8. Zeman, D.H. 1997, The best diagnostic test Swine Health and Production 4:159-160