David Villar

Porcine Circovirus Type 2 (PCV-2) Coinfections in US Field Cases of Postweaning Multisystemic Wasting Syndrome (PMWS)

The prevalence of different pathogens detected in combination with porcine circovirus type 2 (PCV-2) was studied retrospectively in field cases of postweaning multisystemic wasting syndrome (PMWS) diagnosed at the Iowa State University Veterinary Diagnostic Laboratory, Ames, Iowa, between January 2000, and September 2001. The presence of PCV-2 antigen in lymphoid tissues and/or lung, demonstrated by immunohistochemistry, together with moderate to severe lymphoid depletion and/or granulomatous lymphadenitis, was used as the criteria for the diagnosis of PMWS. A total of 484 cases fulfilled these criteria. Most of the cases (294/369) of PMWS occurred in pigs between the ages of 8 and 18 weeks, with a peak at 10 weeks of age. Porcine reproductive and respiratory syndrome virus was detected in 51.9% of the cases, Mycoplasma hyopneumoniae in 35.5%, bacterial septicemia in 14.0%, bacterial pneumonia in 7.6%, swine influenza virus in 5.4%, and PCV-2 alone in 1.9%. In cases with bacterial septicemia the most frequently isolated pathogen was Streptoccocus suis. In cases with bacterial pneumonia, Pasteurella multocida was the most prevalent.

Evaluation of the single cervical skin test and interferon gamma responses to detect Mycobacterium bovis infected cattle in a herd co-infected with Mycobacterium avium subsp. paratuberculosis.

This study reports the performance of the single intradermal tuberculin (SIT) test and the interferon-gamma (IFN-γ) assay for Mycobacterium bovis in a cattle herd with high prevalence of paratuberculosis (PTB). A total of 58/350 animals were selected for necropsy based on one or more of the following criteria: positive to SIT, IFN-γ, a breeding cow that seroconverted to PTB and showed signs compatible with a wasting disease. Infection status was determined by post mortem diagnostic tests that included histopathology examination, mycobacterial cultures and PCR identification for M. bovis and Mycobacterium avium subsp. paratuberculosis (MAP). In 7/58 animals primary tuberculosis (TB) lesions, affecting only the retropharyngeal and/or mediastinal lymph nodes, were found; 3/7 animals were found SIT positive. PTB was confirmed in 35/58 animals, of which 30 had seroconverted and 14 had typical clinical signs. 45/58 animals were IFN-γ(+) using the most stringent criterion (cut-off point ≥ 0.05); however, IFN-γ test was only positive in 33 animals when using a higher threshold (cut-off point ≥ 0.1). Three animals co-infected also showed extensive TB and diffuse PTB lesions. These results show that the combined use of SIT and IFN-γ, as interpreted using official guidelines, detected all confirmed cases of TB. Individually, the sensitivity of the SIT was inadequate to diagnose TB-positive animals with an advanced stage of PTB. The large number of IFN-γ(+) animals with no visible TB lesion could be due, in part, to some protection conferred by prior infection with MAP.

Loss of in vitro Efficacy of Topical Commercial Acaricides on Rhipicephalus microplus (Ixodida: Ixodidae) From Antioquian Farms, Colombia.

ABSTRACT In Antioquia, the problems to control Rhipicephalus microplus (Canestrini, 1888) tick infestations have spread and ranchers claim conventional treatments are no longer effective. In this study, the in vitro efficacy of commercial topical products was tested with ticks obtained from two dairy farms in Antioquia with severe repeated infestations. About 800 engorged ticks were collected directly from animals in two separate visits at the beginning and end of the same month. The adult immersion test was used, which exposed groups of 40 ticks from each collection at the recommended concentration for five commercial products and combinations for 5 min. Efficacy was determined by comparing the reproductive index (fecundity × fertility) of each treated group to that of the control group. The values of all reproductive parameters obtained with ticks from the two collection dates were very similar. Cypermethrin (150 ppm) and amitraz (208 ppm) separately showed very low efficacies of only 10–20% at one farm, and zero at the other. The combination of chlorpyrifos + cypermethrin was the only product with an efficacy >50% at both farms and field observations corroborated to be still capable of eliminating infestations. Exposure to fluazuron at concentrations ranging from 0.05 to 500 ppm for 1 min reduced fertility in all groups by ≥99%, as would be expected for very susceptible strains. However, reduction of oviposition only occurred at the 500 ppm concentration. In conclusion, there is a high degree of resistance to all products tested except for fluazuron.

Plasma and Brain Cholinesterase in Methomyl-Intoxicated Free-Ranging Pigeons (Columba Livia f. Domestica)

A mortality event caused by exposure to the carbamate insecticide methomyl was diagnosed in several hundred pigeons fed treated corn kernels in a city park. A cholinesterase inhibitor insecticide was initially suspected based on clinical signs and a significant inhibition (P < 0.05) of brain cholinesterase (ChE) activity compared with normal values for the species. However, brain ChE activity was within the normal range in birds subsequently submitted in an advanced stage of autolysis. Two groups of 10 healthy pigeons were allocated into a control group and an experimental group, which was offered corn samples retrieved from the incident site. Within minutes of ingesting the contaminated corn, the birds became immobile, had transient wing fluttering, and developed profuse salivation immediately followed by death. Plasma ChE activity at death had declined by more than 95% of preexposure levels (0.04 ± 0.02 vs. 1.56 ± 0.23 μmol/min per milliliter). Brain activity in the sagittal brain sections that were immediately frozen after death was inhibited by ≥50% of control birds (13.5 ± 2.2 vs. 27.5 ± 1.8 μmol/min per gram). However, the sagittal sections left for 1.5 days at ambient temperature of 25°C had normal or higher activity, an effect that was attributed to a combination of spontaneous reactivation and dehydration. After incubation of both plasma and brain homogenates for 1 hr at 37°C, ChE activity recovered by 2- and 1.46-fold, respectively. An organophosphorus and carbamate screen conducted by 2 independent laboratories identified and quantified methomyl in treated kernels at 400 ppm. These results indicate that spontaneous reactivation and dehydration can mask previous reductions in ChE activity.

Interleukin-4, interleukin-5, and interleukin-13 gene expression in cultured mononuclear cells from porcine circovirus type 2-vaccinated pigs after cells were challenged with porcine circovirus type 2 open reading frame 2 antigen

OBJECTIVE To characterize the kinetics of interleukin (IL)-4, IL-5, and IL-13 secretion in peripheral blood and lymph node mononuclear cells isolated from porcine circovirus type 2 (PCV2)-vaccinated pigs after cells were challenged with PCV2 open reading frame 2 antigen. ANIMALS 10 pigs. PROCEDURES 5 pigs were vaccinated with a PCV2 vaccine and received a booster dose 3 weeks later. They were kept together with a similar group of 5 nonvaccinated pigs that served as controls. One week after the second vaccination, peripheral blood mononuclear cells (PBMCs) and excised retropharyngeal lymph node mononuclear cells (LNMCs) were isolated and cultured. Cells were then challenged by exposure to PCV2 open reading frame 2 and evaluated at 2, 12, 24, and 48 hours to determine the expression of IL-4, IL-5, and IL-13 via quantitative PCR assay. Changes in gene expression were analyzed relative to the results from analysis of the sample at 0 hours (calibrator). RESULTS All ILs were upregulated differently in LNMCs and PBMCs from vaccinated pigs. Lymph node mononuclear cells from vaccinated animals produced significantly more IL-4 mRNA than did PBMCs at 2, 12, and 48 hours (relative change: 2.8 vs -3.6, 13.0 vs 3.6, and 9.8 vs 1.8, respectively) and more IL-5 mRNA at 2, 12, 24, and 48 hours (relative change: 1. 2 vs -4.8, 2.2 vs 0.2, 3.2 vs -1.9, and 4.0 vs -3.6, respectively). Interleukin-13 mRNA reached its highest concentration at 24 hours but was 11.9-fold higher in PBMCs than in LNMCs. CONCLUSIONS AND CLINICAL RELEVANCE Results supported the importance of IL-4, IL-5, and IL-13 in pigs, suggesting that PBMCs and LNMCs express cytokines in a tissue-specific manner.

A preliminary survey of Trichinella spp. in pigs raised under controlled housing conditions in Colombia: 2014–2016

A preliminary survey of Trichinella spp. infection was conducted in Colombian swine herds between 2014 and 2016. A total of 1,773 pigs reared on farms under controlled housing conditions and processed in 34 slaughterhouses were tested either by the artificial digestion of pooled muscle samples (n = 1,173) or by serology (n = 600). In addition, 550 rats trapped on 29 swine farm premises were also tested by artificial digestion. No positive pig samples were detected. Similarly, no Trichinella spp. muscle larvae were detected in rats. These results are in agreement with the lack of historical Trichinella infection reports in domestic and wild animals and humans in Colombia. However, a more extensive epidemiological investigation and a continuous surveillance program are needed to continue declaring swine herds in Colombia free of Trichinella infection.

Survey of gastrointestinal parasites, liver flukes and lungworm in feces from dairy cattle in the high tropics of Antioquia, Colombia

A cross sectional study was undertaken to determine the prevalence and intensity of parasitic infections in dairy cattle in the high tropics of Colombia. A total of 1003 rectal samples were collected from dairy cows at 29 farms between May and June 2014 to represent the number of farms, age groups, and size of the 65,000-cow population in the municipality of San Pedro de los Milagros. Coprological techniques were used to detect gastrointestinal nematodes, liver flukes, coccidian oocysts, and first larval stage counts of Dictyocaulus viviparus. In order of decreasing prevalence, the following parasites were detected: coccidial oocyst (36.7%; 95% CIs, 31.6–42.7), strongyle nematodes (31.6%, 27.8–35.4), liver flukes (30.9%, 21.5–37.5), cestodes (8.4%, 7.1–9.7), and D. viviparus (5.4%, 3.4–7.5). Co-infections by all possible combinations of the three most predominant groups occurred in 11 to 15% of the animals. There were significant differences in infection rates between age groups, with higher risk of liver fluke infection in animals older than 1 year of age (odds ratio (OR) = 3.2), but lower presence for coccidia and strongyles (OR = 0.19 and 0.51, respectively). For Fasciola hepatica, within-herd prevalences of > 25% in 16 farms and 94 of 281 (33.5%) animals with > 5 eggs per gram (epg) indicate that significant production losses are likely occurring. The variation in the prevalence of gastrointestinal parasites and liver flukes, together with the level of infection among age groups, could be used in integrated management programs to establish selective anthelmintic treatments and select for heritable traits of host resistance. These results serve as a baseline for future studies to determine the success of control measures and should increase awareness that subclinical parasitism is widespread in the livestock sector.

Case Report—Myonecrosis in Feedlot Cattle

This report describes an outbreak of disease in a Northwestern Iowa feedlot from January to March of 2001. The cattle had been received in the feedlot in July and August, 2000. Clinical signs included severe lameness, recumbency and death. Lameness was not apparent early in the outbreak and the initial diagnosis was central nervous disease. No infectious or toxic cause could be demonstrated. Due to poor performance, approximately a third of the heifers were held back after the main group was sold. Half of these poor performing heifers displayed visible stiffness. Myonecrosis was demonstrated by significantly elevated serum creatine kinase concentrations in visibly affected cattle as compared to visibly unaffected cattle. Histological lesions were confirmed in cardiac muscle but skeletal muscle was not examined. The cattle had been fed a predominantly corn diet with a liquid supplement containing vitamin E calculated at 12.5 IU/head per day until late in the feeding period, when they were switched to a dry supplement delivering 40 IU/head per day. Serum and liver vitamin E concentrations in sampled animals were below the normal range. Common limitations in field investigations include a failure to test un-affected animals to enable comparisons between groups, testing of animals after disease onset resulting in an inability to demonstrate a temporal relationship between the cause and effect, and small sample sizes. Our case-report suffers to some extent from all these factors; however we suspect that the myonecrosis likely occurred due to Vitamin E deficiency. This presumptive diagnosis is based on the combination of knowledge of vitamin E, creatine kinase, (CK) and Aspartate Amino Transferase (AST) values in the sampled cattle, clinical signs observed, elimination of other possible etiologies and supportive statistical analyses. Investigation of unexplained debilitation in feedlot cattle, especially when accompanied by lameness, should include evaluations of serum and/or liver vitamin E concentrations, serum (AST) and (CK) concentration, muscle histology, and ration vitamin E concentration. Introduction This case report involves high death loss encountered by a Northwestern Iowa feedlot from January to March of 2001. The winter of 2000-2001 was characterized in Iowa by muddy pen conditions due to multiple precipitation events combined with freeze-thaw cycles. A weather summary for this area during this time period is presented in Table 1. Case History Between January 23 and March 3, 2001, 27 (6.2%) of 438 yearling feeder heifers in a northern Iowa feedlot died. The heifers were predominantly medium framed, British and Continental breeds. The heifers arrived as separate shipments on July 6, August 12 and August 16 of 2000 from 3 origins in the North Central US. In the same feedlot from February 12 to February 27, 2001, 6 of 159 yearling steers (3.7%) died. The steers were medium framed, apparently of Angus breeding and arrived August 17, 2000 from Nebraska. All of the cattle would have been classified as high quality, northern calves on arrival. Although they initially had good winter hair coats, muddy pen conditions led to extensive hair loss on the abdomen, chest, and legs. In addition to the mortalities, four heifers and a steer with limited recovery were sold for salvage value during January and February, 2001. Three pens of unaffected cattle were received as calves on October 20 November 5, and November 6, 2000. Presenting clinical signs were an initial period of ambulatory difficulty followed by recumbency, then death within a few days. Rectal temperatures in affected animals were subnormal. Early in the period of death loss, a high prevalence of epistaxis was reported in the heifers. Necropsies of several initial cases by the referring veterinarian showed no visible lesions. These findings, combined with apparent altered mental status and seizuring of some of the affected animals, led to an initial diagnosis of Central Nervous System (CNS) disease. Response to antimicrobial, antiinflammatory, and thiamine therapy was poor, as all cases either died or were sold for salvage value after partial recovery. The heifers were housed in two, open, dirt floor feeding pens with shaded concrete bunks and aprons. A shed was available to one heifer pen during the entire feeding period and through January for the other pen. The steers were housed in one pen similar to the heifer pens, but with no available shed. Wet corn gluten feed had been part of the diet until it was removed on January 29 due to the possibility of excess sulfur Iowa State University Animal Industry Report 2006 in the ration contributing to polioencephalomalacia. The ration varied over the period reported, but after exclusion of the wet corn gluten feed consisted of 83% corn, 11% ground corn stalks, 4% liquid protein supplement, and 2% soybean meal on an as-fed basis. The liquid supplement was added to the ration at a rate calculated to achieve an intake of 1.25 lbs/day per animal. According to the manufacturer’s label, this supplement included a minimum of 50% crude protein (with not more than 48% equivalent crude protein units from non-protein nitrogen), a minimum of 40,000 IU vitamin A per pound and a minimum of 10 IU vitamin E per pound. The liquid supplement was discontinued on February 17, 2001 due to initial consideration of possible monensin or urea toxicity, and was replaced by a dry supplement containing 40 IU vitamin E per pound. The dry supplement was included in the feed at 1 lb/day per animal, which was maintained for the remainder of the feeding period. Harvest shipment dates for the first two groups of heifers (unaffected heifers with the best performance) were February 27, 2001 (176 head) and March 4, 2001 (86 head). Approximately 50% of the remaining heifers displayed visible lameness. The steers had not been shipped as of a site visit on March 9, 2001, but were nearing finish. Approximately 30% of the steers were estimated to be lame at this time. Diagnostic Findings A live heifer in a terminal stage was submitted to the Iowa State University Diagnostic Lab on February 12, 2001. At this time, 9 heifers (including this animal) and 1 steer had died after displaying typical clinical signs. Pertinent diagnostic laboratory findings were: Histology: No significant lesions in brain, spinal cord, liver, kidney, heart Bacteriology: No bacterial growth from brain, liver, or kidney Two additional heifers were submitted on February 15, 2001 with a history of rapid deterioration and death. Laboratory findings were as follows. Gross findings: Heifer 1 Fibrin clots in enlarged right hock, “old” rumen ulcer, rumen pH 5.4, Heifer 2 Catarrhal exudate and ulcers in abomasum, clumped rumen papillae, rumen pH 5.6 Histology: Brains: Mild hyalinization of scattered vessels, mild endothelial swelling, Hearts: Mild, subtle, multifocal acute myofibrillar necrosis and hyalinization, Rumens: Edema in papillae, multifocal suppurative inflammation, Abomasums: Multifocal hemorrhages, Bacteriology: Arcanobacterium pyogenes from the hock of heifer 1. Immunohistochemistry: Negative for BVD. Toxicology: Testing ruled out urea toxicosis (by feed and rumen content analysis), excess sulfur (by analysis of feed and water submissions), nitrate poisoning (ocular fluid), hypomagnesemia (ocular fluid). Copper and selenium concentrations in the livers were within normal limits. Analysis of two supplement samples confirmed the monensin concentration was not above specifications. Serum from a heifer in the early stages of disease (ambulatory difficulty but still standing) was also submitted on February 15. The serum creatine kinase (CK) concentration was 23,960 IU/L. The expected upper range of normal is 350 IU/L. The case fatality rate in the affected pens continued to be reported as almost 100% although clinical success with thiamine on similar appearing cases in an adjacent pen of calves was reported. At this time, the owners were unwilling to pursue further diagnostic tests, so a combination of research funds from the authors and support from the Diagnostic Laboratory was used to continue the investigation. On March 1, 2001, one live-affected and three dead animals were submitted to the diagnostic lab. In addition, whole blood and serum from an animal that was still alive and standing at the feedlot were submitted. Including these animals, 26 heifers and 6 steers had been lost to date. Results were as follows. The live heifer was conscious but unable to rise from lateral recumbency. It received treatment for CNS disease but died on the afternoon of the next day. Nystagmus was noted on physical examination. Analysis of a cerebral spinal fluid tap reported cellularity within the normal range, high protein content and negative bacterial culture. The entire spinal cord was extracted and no gross or histological lesions were noted. Brain sodium levels were slightly elevated but not enough to suggest salt toxicity. The slightly elevated brain sodium levels were considered due to dehydration. Clinical Pathology: The serum creatine kinase value of the animal at the feedlot was 48,952 IU/L. Histology: Hearts from two animals showed a few scattered foci of myofiber loss and replacement with fibrous connective tissue. Chemistry/toxicology: Vitamin E and selenium analysis results from two livers submitted March 1 and one liver submitted February 15 are reported in Table 2. Iowa State University Animal Industry Report 2006 A site visit was conducted on March 5, 2001 prior to laboratory results from the March 1 submissions. The first two harvest shipments of heifers had been completed by this time and only the poorest performing heifers remained. The disease history was clarified at this time. Approximately 50% of the heifers and 30% of the steers in the affected groups appeared to be lame. The typical stance of the severely affected animals is represented in Figure 1. Affected animals