Haemophilus parasuis (Glasser disease) - Culture; Molecular diagnosis (PCR); Molecular typing serovars-serotypes by sequencing.
Haemophilus parasuis is a gram - negative coccobacillus pleomorphic 1 to 7 microns x 0.2 to 0.7 microns, still, non - hemolytic, NAD dependent for its development, the genus Haemophilus, Pasteurellaceae family. Haemophilus parasuis has a worldwide distribution, although it is found more frequently in countries of pig farms. This organism is considered an animal pathogen of pigs, which causes Glässer's disease, a disease with a high mortality rate. 15 described serovars or serotypes of Haemophilus parasuis, which are the most virulent serovars 1, 4, 5, 10, 12, 13 and 14. This bacterium has importance as causing fibrinous polyserositis and polyarthritis swine disease ( Glässer). It is considered and the most economically important infections in pig farms for the cost of antibiotic treatments and loss of animals.
Haemophilus parasuis transmission occurs horizontally, through direct contact between healthy and sick animals via the airborne route, or vertically through mothers piglets during the lactation period. The air is likely to play a role in spreading distance. The respiratory tract is the gateway of Haemophilus parasuis, from where it can diffuse throughout the body. This bacterium colonizes the upper respiratory tract of animals, although under appropriate conditions can invade the whole organism. Once colonizes the nasal mucosa, it binds to the epithelial cells and induces apoptosis of these cells and then subsequently passed to the lung. Virulent strains that resist attack by lung macrophages, pass into the blood, and through this the brain and joints, also reaching the serosal surfaces of different bodies.
Haemophilus parasuis is particularly problematic in the respiratory tract. This bacterium frequently isolated upper respiratory tract of pigs, without their presence necessarily entails an acute infection. In the lung, this microorganism generally behaves as an opportunistic infectious agents or other situations of immune suppression. Clinical disease mainly affects young animaqles under stress, and can cause acute infection when introduced into a herd that has not been previously exposed. The animals most affected are the small pigs from 4 to 6 weeks. When infection courses symptomatically clinical signs include high fever, lethargy and anorexia. Depending on the location, it can manifest through other clinical signs, such as abdominal breathing, dyspnea, intense coughing, chest pain and abdomen, swollen joints (especially carpal and tarsal), lameness, tremors, incoordination, lateral decubitus and cyanosis. Chronic infections can cause poor performance and symptoms such as extreme thinness, cough, dyspnea, weight loss, lameness and erisado coat. Furthermore, it is common the presence of lesions as fibrinous bronchopneumonia rhinitis, purulent meningitis, fibrinous arthritis and fibrinous pericarditis can be accompanied by hydropericardium. When it causes acute septicemia, usually fatal in about 2 days.
Haemophilus parasuis has been identified mostly in animal between two weeks and four months old, causing high rates of mortality and morbidity in holdings that have not been in previous contact with this agent, affecting animals in any of the production phases.
Recommended tests for diagnosis:
The diagnosis is considered difficult and poor performance. Culture isolation, is generally considered by the fastidious growth infectivity of this bacterium, in addition to being affected by the previous antibiotic therapy should have been administered. Moreover, the overgrowth of other contaminating bacteria in the sample, especially if the samples are not taken and / or transported properly. If isolated in culture, you are required by biochemical identification to differentiate from other bacteria nonhemolytic also dependent NAD as Actinobacillus indolicus, Actinobacillus porcinus and Actinobacillus minor, among other tests. These tests are laborious and time consuming . For these reasons being imposed molecular methods (PCR), which also detect the 15 serovars sequencing the capsular locus, sets all serovars except serovars 5 and 12. The molecular process is faster, more sensitive and more specific tests indirect hemagglutination.
Tests in IVAMI:
- Detection by isolation by culturing in selective media.
- Molecular diagnosis (PCR), to detect DNA of Haemophilus parasuis.
- Molecular Identification of serovar (except 5 and 12).
- Nasal exudate (nasal swab).
Preservation and shipment of sample:
- Refrigerated (preferred) for less than 2 days.
- Frozen: over 2 days.
- Cultivation: 48 to 72 hours.
- Molecular diagnosis (PCR): 24 to 48 hours.
Cost of the test: