Agar Gel Precipitation Research Articles

Seroprevalence of low pathogenic avian influenza (H9N2) and associated risk factors in the Gyeonggi-do of Korea during 2005-2006

Between November 2005 and March 2006, a total of 253 poultry flocks in the Gyeonggi-do of Korea were examined for seroprevalence against avian influenza (AI) using a hemagglutination inhibition (HI) test and an agar gel precipitation test. No low pathogenic avian influenza (LPAI) virus was isolated from 47 seropositive flocks that lacked clinical signs during sampling. The unadjusted percentage of seroprevalence rates of layer and broiler flocks were not significantly different, i.e., 26% (25/96) and 23% (22/97), respectively. The HI titer of the layers (mean = 89) was higher than the broilers (mean = 36; p < 0.001). A cross-sectional study was conducted for the seroprevalence of LPAI in the layers. Of 7 risk factors, farms employing one or more workers had a higher seropositive prevalence as compared to farms without hired employees (adjusted prevalence OR = 11.5, p = 0.031). Layer flocks older than 400 d had higher seropositivity than flocks younger than 300 d (OR = 4.9, p = 0.017). The farmers recognized at least one of the clinical signs in seropositive flocks, such as decreased egg production, respiratory syndromes, and increased mortality (OR = 2.3, p = 0.082). In a matched case-control study, 20 pairs of case and control flocks matched for type of flock, hired employees, age, and flock size were compared. Frequent cleansing with disinfectants was associated with a decreased risk of seropositivity (OR = 0.2, p = 0.022). Although there was a low statistical association, using a foot disinfectant when entering the building led to a decreased rate of seropositivity (OR = 0.3, p = 0.105).

Prevalence of contagious bovine pleuropneumonia in Borno State, Nigeria

Epidemiological situation of contagious bovine pleuropneumoia (CBPP) over a ten (10) year period in Borno State of Nigeria was examined. During this period, 1,178 out of 355,745 cattle examined at postmortem had lesions suggestive of CBPP giving an overall prevalence rate of 0.33%. Highest prevalence rate of 0.77% was recorded in 1988 while lowest prevalence rate of 0.08% was recorded in 1994. Total vaccination coverage during the same period was 2,344,520 with highest vaccination coverage of 488,054 (10.8%) in 1988 and the lowest coverage of 66,398 (1.5%) in 1997. A total of 37 outbreaks of CBPP were reported during the period under review with highest outbreak (8) occurring in 1990. Seasonal prevalence of the disease was found to be highest in rainy season (0.20%) than the dry season (0.13%) but was not statistically significant (P>0.05). In a related development, a total of 3,875 cattle were examined between January and July 1998 in an attempt to find the incidence of CBPP using agar gel precipitation test (AGPT). Out of 57 suspected lungs, 41 (1.1%) were positive for AGPT. The disease is still endemic in Borno State and vaccination coverage was grossly inadequate. Keywords: CBPP, cattle, AGPT, prevalence, vaccination Nigerian Veterinary Journal Vol. 27 (2) 2006: pp. 14-22

Application of Polymerase Chain Reaction Fingerprinting to Differentiate Ornithobacterium Rhinotracheale Isolates

Ornithobacterium rhinotracheale (ORT) is an infectious respiratory pathogen of chickens, turkeys, and wild birds. There are 18 serotypes of ORT reported worldwide. In this study, enterobacterial repetitive intergenic consensus (ERIC) polymerase chain reaction and random amplified polymorphic DNA assay with Universal M13 primer-based fingerprinting techniques were investigated for their ability to differentiate ORT isolates. The authors examined 50 field isolates and 8 reference strains of ORT for their genetic differences. The fingerprint patterns were compared with serotyping results of ORT by the agar gel precipitation test. M13 fingerprinting revealed different patterns for 6 reference serotypes of ORT that were tested, namely, C, D, E, I, J, and K. Ornithobacterium rhinotracheale reference serotypes A and F yielded indistinguishable fingerprints with M13 fingerprinting. The ERIC 1R technique discerned only 5 of the 8 reference serotypes of ORT. Distinct fingerprints were also found within the ORT serotypes with both techniques. From 58 isolates of ORT that were fingerprinted belonging to 8 ORT serotypes, 10 different fingerprints were obtained with M13 fingerprinting and 6 different fingerprints were obtained with ERIC 1R fingerprinting. M13 fingerprinting technique was found to be more discriminative in differentiating ORT isolates than the ERIC 1R fingerprinting technique. These results suggest that fingerprinting techniques may be a more discerning tool for characterizing ORT isolates than the serological test using the agar gel precipitation test. This fingerprinting technique could potentially be a valuable tool in identifying an isolate from a clinical outbreak of ORT infection for development of an autogenous vaccine.

Detection and Seroprevalence of Infectious Bronchitis Virus Strains in Commercial Poultry in Pakistan

This study was conducted to investigate the incidence of infectious bronchitis virus (IBV) in commercial broiler and layer flocks in Pakistan. Serum samples from 16 layers and 9 broiler flocks were screened against M-41, D-274, D-1466, and 4-91 strain antigens using hemagglutination inhibition assay. Overall, 88% of the flocks were seropositive for M-41 antibodies, whereas 40, 52, and 8% of the flocks were positive for D-274, D-1466, and 4-91 IBV strains, respectively. The M-41 antigen was also detected in lungs and tracheal tissues of the clinically positive infectious bronchitis cases. Phospholipase C treatment of the lung and tracheal tissue homogenates from IBV-positive chickens increased the detection limit for M-41 strain from 1.3% positive samples in simple hemagglutination assay to 30.6% positivity when the same samples were treated with phospholipase C. Similarly, reverse transcription-PCR was a much better M-41 detection tool as compared with the classical agar gel precipitation assay utilized to screen tissue homogenates from IBV-positive chickens. In conclusion, this survey clearly demonstrates that several strains of IBV are prevalent in poultry flocks in Pakistan. By utilizing such diagnostic techniques it is possible to conduct a detailed epidemiological study to determine the full economic impact of this disease.

Molecular characterization of field isolates and vaccine strains of infectious bursal disease virus

The present investigation was conducted to study the genetic heterogenicity and molecular polymorphism among the field isolates and vaccine strains of infectious bursal disease virus (IBDV). Samples of bursa of Fabricius from 15 suspected outbreaks of infectious bursal disease (IBD) were subjected to agar gel precipitation test (AGPT), virus isolation and reverse transcription-polymerase chain reaction (RT-PCR) combined with restriction fragment length polymorphism (RFLP). Nine out of 15 samples were found positive in AGPT while 14 were found positive both by virus isolation and RT-PCR. PCR amplified 474bp fragment from the variable region of VP2. Sac I, Stu I, Alu I, Ssp I and Mbo I restriction enzymes were used for characterization of all the 14 IBDV isolates and four reference vaccine strains. Sac I, Stu I, Alu I and Ssp I could differentiate classical virulent IBD (cvIBD) vaccine virus strains from very virulent IBD (vvIBD) field isolates by their varying restriction patterns. Based on above results two field isolates (VPL and VMK) were placed in cvIBD virus group and 12 field isolates were placed in vvIBD virus group. Virus neutralisation test (VNT) using rabbit raised Georgia strain anti-serum, however, could not differentiate between cvIBD virus and vvIBD virus. It was concluded that RT-PCR combined with RFLP assay using restriction enzymes Sac I, Stu I, Alu I and Ssp I can be used for rapid differentiation and classification of field isolates of IBDV.

Analyses of the results of different test systems in the 2005 global proficiency testing schemes for infectious bursal disease virus and Newcastle disease virus antibody detection in chicken serum

The results of global proficiency testing schemes (PTS) for serological tests to detect antibodies against infectious bursal disease virus (IBDV) and Newcastle disease virus (NDV) in chicken serum, in which 125 and 120 laboratories, respectively, participated from Africa, Asia, Europe, Central and South America, were used to analyse the performances of different antibody test systems such as virus neutralization tests, haemagglutination inhibition tests, enzyme-linked immunosorbent assays and agar gel precipitation tests. All laboratories were asked to carry out their routine diagnostic tests for the detection of IBDV and NDV antibodies as usual. This global ring trial provided a large amount of data on variation within and between laboratories and test systems used worldwide. The data showed that the variation between the quantitative test results of different laboratories (R between) using the IBDV virus neutralization tests and the NDV haemagglutination inhibition test was higher (about double) compared with the variation within commercial enzyme-linked immunosorbent assay systems. Although both tests are often referred to and used as the “gold standard” in experimental and scientific studies, official procedures and for the validation of tests, this study shows that there is an urgent need for a global implementation of recommended test procedures and/or the inclusion of international reference sera in these studies.

Isolation of Actinobacillus pleuropneumoniae Serovar 15-Like Strain from a Field Case of Porcine Pleuropneumonia in Japan

An Actinobacillus pleuropneumoniae strain isolated from a field case of porcine pleuropneumonia in Japan, was closely related to a reference strain of serovar 15, which is a newly proposed serovar according to an analysis of field isolates originating from Australia. The isolate had biological and biochemical properties consistent with A. pleuropneumoniae biovar 1, and reacted strongly to a rabbit antiserum raised against a reference strain of serovar 15 in an agar gel precipitation test. The nucleotide sequence of a hyper variable region in the 16S RNA gene of the isolate was identical to that of the reference strain of serovar 15. The isolate possessed A. pleuropneumoniae-RTX toxin (Apx) II, III, and IV genes, consistent with serovar 15. Its virulence in mice was lower than that of ApxI-bearing strains but higher than that of other ApxIII-bearing strains. This is the first report describing the isolation of A. pleuropneumoniae serovar 15-like strain from a country or region other than Australia.

Development and Use of Fowlpox Vectored Vaccines for Avian Influenza

The avian influenza (AI) vaccine designated TROVAC-AIV H5 (TROVAC-H5) contains a live recombinant fowlpox rec. (FP) recombinant (recFP), expressing the hemagglutinin (HA) gene of an AI H5 subtype isolate. This recombinant vaccine was granted a license in the United States for emergency use in 1998 and full registration in Mexico, Guatemala, and El Salvador where over 2 billion doses have been administered. One injection of TROVAC-H5 protects chickens against AI-induced mortality and morbidity for at least 20 weeks, and significantly decreases shedding after challenge with a wide panel of H5-subtype AI strains, regardless of neuraminidase subtype. Recently, excellent protection was demonstrated against 2003 and 2004 Asian highly pathogenic H5N1 isolates. Whereas TROVAC-H5 AI H5 efficacy was not inhibited by anti-AI or anti-fowlpox maternal antibodies (passive immunity), protection to AI was significantly decreased in chickens previously vaccinated or infected with FP (active immunity). Advantages of the TROVAC-H5 vaccine over inactivated AI vaccines are: (a) single administration at 1 day of age and early onset (1 week) of protection, (b) easy monitoring of AI infection in vaccinated flocks with agar gel precipitation (AGP) and enzyme-linked immunosorbent assay (ELISA) used as tests to differentiate infected from vaccinated animals (DIVA tests), and (c) no residue problem due to adjuvant. These features make TROVAC-H5 an ideal AI vaccine for routine administration of day-of-age chicks in hatcheries. RecFP expressing HA from three lineages of H7 subtype (Eurasian, American, and Australian) were also tested for efficacy against a highly pathogenic avian influenza (HPAI) Eurasian HPAI H7N1. Only the recFP expressing the Eurasian H7 gene provided sufficient protection indicating that the breadth of protection induced by recFP is apparently restricted for H7 isolates. The fowlpox vector technology can also be used for the production of an emergency vaccine: once the HA sequence of an emerging AI virus is known, recFP can be rapidly generated. TROVAC-H5 has recently been shown to be immunogenic in cats and could therefore also be considered for use in mammals.

Inactivation of infectious bursal disease virus by binary ethylenimine and formalin

In this experiment conducted to study the inactivation dynamics of infectious bursal disease virus (IBDV) by binary ethylenimine (BEI) in comparison with formalin, IBDV was isolated from the bursa of infected chickens and its confirmation was done by agar gel precipitation test. Viral suspensions were subjected to inactivation with BEI and formalin for pre-set time intervals. BEI was employed at concentrations of 0.001 and 0.002 mol/L while formalin was used at 0.1% and 0.2%. Sampling was done at 6, 12, 24, 36 and 48 h of incubation and samples were tested for their inactivation status in 9-day-old embryonated eggs and 3-week-old broiler chickens. IBDV was completely inactivated by 0.001 and 0.002 mol/L BEI after 36 h of incubation at 37 degrees C, whereas formalin at 0.1% and 0.2% concentrations inactivated IBDV in 24 h.

Isolation of Lumpy skin disease virus form naturally infected cattle previously vaccinated with live attenuated sheep poxvirus vaccine

Lumpy skin disease virus (LSDV) was isolated, from naturally infected cattle that have a history of previous vaccination with live attenuated sheep pox virus (SPV) vaccine. The virus was isolated on chorio-allantoic membrane (CAM) of specific pathogen free (SPF) embryonated chicken eggs (ECE) and identified by agar gel precipitation test (AGPT) and neutralization test using specific hyperimmune serum against LSDV and SPV. Characteristic intracytoplasmic inclusion bodies was detected in trypsenized cell of infected CAM stained with H&E. Laboratory studies for characterization of isolated LSDV revealed that it was stable at a wide range of pH, but it was inactivated by exposure to 56 0C for 15 minutes. Treatment of isolated LSDV with lipid solvents (20% ethyle ether and chloroform) reduced the virus titer 3.2 and 4.4 log respectively after 24 hrs at 4 0C .On cross neutralization testcomplete neutralization of isolated LSDV was obtained with both reference LSDV and SPV antisera. Cattle vaccinated with live attenuated SPV vaccine under experimental condition found to be protected against natural field infection with LSDV.

Serological and Virological Studies of Newcastle Disease and Avian Influenza in Slaughter-Age Ostriches (Struthio camelus) in Japan

Serum samples from 191 ostriches (Struthio camelus) in Japan were tested for antibodies to Newcastle disease virus (NDV) and avian influenza virus (AIV). Twenty-two (12%) contained NDV-specific neutralizing antibodies by a virus-neutralization (VN) test without vaccination. Antibodies to AIV were not detected in the any sera by an agar gel precipitation test. Seven serum samples that had vaccinated with live NDV by eye drop were all positive by the VN test at 1 month post vaccination. A haemagglutination inhibition (HI) test for NDV seemed not to be suitable for ostriches because of non-specific agglutination of chicken red blood cells. No haemagglutinating viruses were isolated. This is the first report on detection of antibodies against NDV in ostriches in Japan.

Passive immunization using purified IgYs against infectious bursal disease of chickens in Pakistan

Infectious bursal disease (IBD) is an acute and highly contagious disease of young chickens caused by Birnavirus. Mortality of infected birds can be best prevented if injected with antibodies. The present study was an attempt to raise specific hyper-immune polyclonal antibodies against IBD virus in Pakistan. Commercial layers divided into four groups were injected with IBD vaccine subcutaneously according to four different treatment regimens. Eggs were collected daily and antibodies were purified from yolk with dextran sulphate. Titers of antibodies in serum and yolk were evaluated with enzyme linked immunosorbant assay and agar gel precipitation test. Antibody titers were significantly higher in yolk than serum. Eggs collected at 28 days post-vaccination had maximum antibody titers. Of treatment regimens, T3 was found to be most effective for hyperimmunization. Lyophilized antibodies stored at 4℃ did not lose their activity till the end of experiment. IBD virus infected birds were injected with purified antibodies which induced 92% recovery as compared to control birds. The study implicates that the purified antibodies may be useful as a therapeutic agent to cure IBD infected birds.

Reverse Transcriptase-Polymerase Chain Reaction to Detect Avian Encephalomyelitis Virus

A reverse transcriptase-polymerase chain reaction (RT-PCR) was developed and optimized for the detection of avian encephalomyelitis virus (AEV). A pair of primers was prepared based on the VP2 gene of the structural protein P1 region of the AEV genome. An avian encephalomyelitis virus-specific 619-base pair cDNA product was amplified by these primers from five reference/field strains of AEVs but not from 10 other avian pathogenic viruses and bacteria. The RT-PCR assay developed in this study was found to be sensitive and specific with as little as 10 pg of avian encephalomyelitis virus RNA detected using gel electrophoresis. Furthermore, AEV-RT-PCR was able to detect AE virus from chicken embryo brain at 3 days postinoculation as compared with the AE agar gel precipitation test (AGP), which required up to 11 days of incubation in the embryos.

Development of a One-Step Strip Test for the Diagnosis of Chicken Infectious Bursal Disease

A rapid diagnostic strip for chicken infectious bursal disease (IBD) was developed based on membrane chromatography using high-affinity monoclonal antibodies directed to chicken infectious bursal disease virus (IBDV). The diagnostic strip has high specificity for detection of chicken IBDV antigen and recognizes a variety of the virus isolates, including virulent and attenuated strains, with no cross-reactivity to other viruses, such as Newcastle disease virus, Marek's disease virus, infectious bronchitis virus, infectious laryngotracheitis virus, and egg-drop-syndrome virus. The results showed that its specificity was highly consistent with the agar-gel precipitation test (AGP). The diagnostic strip detected as low as 800 median egg lethal dose (ELD50) viruses in the IBDV BC6/85-infected sample, which was comparable with AC-ELISA (400 ELD50) and 32 times more sensitive than the AGP test (2.56 x 10(4) ELD50). In experimental infection, IBDV was detected in the bursa as early as 36 hr postinfection with the diagnostic strip before the clinical signs and gross lesions appeared. It takes only 1-2 min to do a strip test to detect chicken IBDV antigen after the specimen is grounded in a whirl pack with finger massage.

A rapid assay for detecting antibody against leucocytozoonosis in chickens with a latex agglutination test using recombinant R7 antigen

A method for detecting antibody against leucocytozoonosis in chickens by latex agglutination (LA) was developed using latex beads coated with recombinant R7 (rR7), an outer membrane antigen of second-generation schizonts of Leucocytozoon caulleryi. Compared with the agar gel precipitation test, which is widely used in Japan, LA could detect antibody induced by L. caulleryi infection with greater sensitivity. No agglutination was detected with sera from specific pathogen free or layer chickens that had not been vaccinated with oil-adjuvanted rR7 antigen, or infected with L. caulleryi, nor with sera from chickens inoculated with other pathogens, establishing the specificity of the assay. The LA test was also able to be used to quantify serum antibody induced by vaccination, which is not possible with the agar gel precipitation test. This study has shown that LA using the rR7 antigen is a simple, quick, and useful method for detecting antibody against L. caulleryi.

Comparison of agal gel precipitation test (AGPT) and enzyme linked immunosorbent assay (ELISA) in the detection of infectious bursal disease virus (IBDV) antibody in village chickens ın Oyo State, Nigeria

The use of agar gel precipitation test (AGPT) and enzyme linked immunosorbent assay (ELISA) in assaying for the presence of infectious bursal disease (IBD) virus antibody in village chickens in Oyo State, Nigeria, was compared. Out of 400 sera subjected to ELISA, 360 (90%) samples where positive for IBD virus (Serotype 1) antibody with a titre range of 3,441 to 22,444 whereas, by the AGPT, out of 392 sera tested, 248 (63.3%) samples were positive with a titre range of 0log2 (neat) to 4log2. This study has correctly presented the seroprevalence of IBD in village chickens in this environment and has further confirmed the superior sensitivity of the ELISA technique. Nigerian Veterinary Journal Vol.25(1) 2004: 26-29

An epizootic of equine influenza in Upper Egypt in 2000

This study describes an epizootic of respiratory tract disease caused by influenza virus infection in a large population of equines in Luxor and Aswan, Upper Egypt, during the winter of 2000. The epizootic started in January and the infection rate reached its peak in February before gradually decreasing until the end of April, 2000. Horses, donkeys and mules of all ages and both sexes were affected. Free movement of the infected equines and direct contact between the animals at markets facilitated the rapid spread of the disease. The cause of the epizootic was established by use of serological testing and the identification of the influenza virus in nasal secretions. Egg inoculation and the haemagglutination test were used to detect the influenza virus. Both haemagglutination inhibition (HI) and agar gel precipitation tests were performed to identify the isolated influenza virus using reference antisera against A/Equi-1 (H7N7) and A/Equi-2 (H3N8). Antibodies against the equine influenza virus were demonstrated in 416 (95.6%) out of 435 collected sera using the HI test. High rectal temperature, inappetence, conjunctivitis, redness of nasal mucosa, a serous to mucopurulent nasal discharge and a harsh dry cough were the most common clinical manifestations. Stress factors, such as using equines for heavy transportation and drawing, precipitated the onset of the disease, intensified the clinical syndrome, delayed recovery and facilitated secondary bacterial infection. The present study suggested that the absence of a vaccination programme against equine influenza was one of the principal causes of the spread of infection during this outbreak. In conclusion, the implementation of a national equine influenza vaccination programme, using an effective updated vaccine, is essential in Egypt.

Isolation and characterization of virus of highly pathogenic avian influenza H5 subtype of chicken from outbreaks in Indonesia

A study on the isolation and characterization of Highly Pathogenic Avian Influenza of chicken from outbreaks in Indonesia was conducted at Indonesian Research Institute for Veterinary Science. Outbreaks of avian disease had been reported in Indonesia since August 2003 affecting commercial layer, broiler, quail, and ostrich and also native chicken with showing clinical signs such as cyanosis of wattle and comb, nasal discharges and hypersalivation, subcutaneous ptechiae on foot and leg, diarre and sudden high mortality. The aim of this study is to isolate and characterize the causal agent of the disease. Samples of serum, feather follicle, tracheal swab, as well as organs of proventriculus, intestine, caecal tonsil , trachea and lungs were collected from infected animals. Serum samples were tested haemaglutination/haemaglutination inhibition to Newcastle Disease and Egg Drop Syndrome viruses. Isolation of virus of the causal agent of the outbreak was conducted from samples of feather follicle, tracheal swab, and organs using 11 days old specific pathogen free (SPF) embryonated eggs. The isolated viruses were then characterised by agar gel precipitation test using swine influenza reference antisera, by haemaglutination inhibition using H1 to H15 reference antisera, and by electron microscope examination. The pathogenicity of the viruses was confirmed by intravenous pathogenicity index test and its culture in Chicken Embryo Fibroblast primary cell culture without addition of trypsin. The study revealed that the causative agent of the outbreaks of avian disease in Indonesia was avian influenza H5 subtype virus based upon serological tests, virus isolation and characterization using swine influenza reference antisera, and electron microscope examination. While subtyping of the viruses using H1 to H15 reference antisera suggested that the virus is very likely to be an avian influenza H5N1 subtype virus. The pathogenicity test confirmed that the viruses are highly pathogenic to experimental animals. It is concluded that the causative agent of the outbreaks of avian disease in Indonesia was avian influenza H5 subtype virus. The result has been the basis of further study such as development serological tests and vaccine production. The decission of Indonesian Government to conduct vaccination program using homolog vaccine in order to control the disease is regarded as the correct choice. However, it should be accompanied by conducting surveillance and monitoring of the disease as well as the possibility of mutation of virus. The program should be coordinated nationally. Key words: Virus isolation, characterization, chicken, outbreak, highly pathogenic avian influenza (HPAI), H5 subtype, Indonesia

Detection of Serum Antibody Levels Against Infectious Bursal Disease (IBD) Virus Using Indirect Hemagglutination (IHA) Test in Commercial Broilers

A total of 336 Serum samples were collected from different commercial broiler farms and slaughter shops from in and around Faisalabad. These samples were divided in to three groups according to the age of the birds i.e. 0-3 weeks (86 samples), 3-6 weeks (68 samples) and 6-8 weeks (182 samples). Indirect hemagglutination (IHA) test was used to titrate the serum antibodies against infectious bursal disease virus. Hyper immune serum was raised in laboratory rabbits against IBDV vaccine (D-78). It was used to identify and confirm the IBD virus from bursal tissues isolated from the IBD affected flocks using the qualitative tests i.e. agar gel precipitation and modified counter immuno-electrophoresis. The viral antigen was sonified and used to sensitize the Human O erythrocytes without any coupling agent. 1% sensitized erythrocytes suspension was prepared and used to determine the antibody titer. Results indicated that out of 336 test serum samples 221 (65.77%) were positive. The maximum positive samples belonged to 6-8 weeks of age (78.57%) followed by 3-6 weeks (60.29%) and 0-3 weeks (43.02%), respectively. Calculated geometric mean titers for groups 0-3, 3-6 and 6-8 wks of age, were found to be 6.37, 10.84 and 16.14, respectively.

Characterization of the diversity of Haemophilus parasuis field isolates by use of serotyping and genotyping.

To characterize the genetic diversity of Haemophilus parasuis field isolates with regard to serovar, herd of origin, and site of isolation. Isolates of H parasuis obtained from pigs in 15 North American herds and multi-farm systems. 98 H parasuis isolates were genotyped with the enterobacterial repetitive intergeneic consensus based-polymerase chain reaction (ERIC-PCR) technique and serotyped via agar gel precipitation test. Genomic fingerprints were analyzed and dendrograms were constructed to identify strains from the same serovar group, herd of origin, or isolation site and to evaluate the genetic variability within these categories. Serovar 4 (39%) and nontypeable (NT) isolates (27%) were most prevalent. Thirty-four distinct strains were identified among the 98 isolates, using a 90% similarity cutoff. Strains from serovar 4 and NT isolates had high genetic diversity (12 and 18 strains, respectively). One to 3 major clusters of prevalent strains could be identified in most of the evaluated herds. Haemophilus parasuis strains isolated from the upper respiratory tract were either serovar 3 or NT isolates. Potentially virulent strains (isolated from systemic sites) were either serovars 1, 2, 4, 5, 12, 13, or 14, or NT isolates. Although H parasuis had high genetic diversity overall, only a few strains caused disease in these herds. The ERIC-PCR technique was more discriminative than serotyping, and a broad genetic variety was observed within particular serovar groups.