Correlations between lung pneumonic lesions and serologic status for key respiratory pathogens in slaughtered pigs in northern Uganda

Assessing the antiviral activity of antimicrobial peptides Caerin1.1 against PRRSV in Vitro and in Vivo

The Porcine reproductive and respiratory syndrome (PRRS) causes severe financial losses to the global swine industry. Due to continuous virus evolution, the protection against the PRRS provided by current vaccines is limited. In order to find new antiviral strategies, this study investigated the antiviral potential of antimicrobial peptides (AMPs) against PRRSV. Given the diversity of PRRSV strains and the limited effectiveness of existing vaccines in controlling PRRSV, this study evaluated the inhibitory effects of KLAK, Cecropin B, Piscidin1, and Caerin1.1 on 3 strains of PRRSV (lineage 5 classical strain, lineage 8 highly pathogenic strain, and lineage 1 NADC30-like strain). Caerin1.1 exhibited significant dose-dependent antiviral activity, with an effective concentration (EC50) of 7.5 μM. Caerin1.1 effectively inhibited PRRSV replication when added before or in early infection but showed reduced effectiveness when added in late infection, indicating its potential involvement in targeting early transcription mechanisms of viral RNA polymerase and significantly upregulating cytokine gene expression. In the NADC30 strain-based animal infection model, Caerin1.1 treatment significantly reduced lung viral loads and inflammation in the lungs of PRRSV-infected pigs, with a mortality rate of 0 % (0/5) in the treated group compared to 66.67 % (4/6) in the untreated group, indicating a reduction in the mortality rate. Additionally, compared with the untreated group, the Caerin1.1-treated group showed significant improvements, such as lighter fever, more daily weight gain, less clinical symptoms, less viral load in blood, and less virus oral shedding (P < 0.05). These findings reveal the potential of antimicrobial peptides as PRRSV therapeutic agents and suggest that Caerin1.1 is a promising candidate for a novel anti-PRRSV drug.

Integrative taxonomy of Metastrongylus spp. in wild boars from Brazil

BACKGROUND

Wild boars (Sus scrofa) may cause substantial damage to crops and can spread zoonotic parasites to domestic animals, posing a risk to health and animal production. Metastrongylus spp. can negatively affect the wild boar population, increasing piglet mortality. In addition to that, studies with Metastrongylus genetic characterization are still scarce in Brazil. The present study aims to characterize Metastrongylus spp. from wild boars hunted in the states of São Paulo, Paraná, and Rio Grande do Sul, Brazil, using traditional morphological description and DNA sequences in an integrative taxonomic approach.

METHODS

After nematode collection from 58 wild boars, the parasites were morphologically identified and genetically characterized by the amplification of 18S ribosomal DNA (rDNA), 28S rDNA, internal transcribed spacer (ITS) region, and cox-1 mitochondrial DNA (mtDNA). Descriptors of infection were determined and Pearson's Chi-square test was applied to compare the prevalence of infections among the identified parasite species, host age group (juveniles and adults), and sex. The Mann-Whitney U test was performed to compare the mean intensity between the age groups and sex.

RESULTS

Metastrongylus salmi, Metastrongylus apri, and Metastrongylus pudendotectus were identified in 77.6% (45/58) of the necropsied wild boars. Metastrongylus salmi was the most prevalent and abundant species (70.7%, 11.1), followed by M. pudendotectus (18.9%, 4.3) and M. apri (17.2%, 2.2). Metastrongylus pudendotectus showed the highest mean intensity and range (25.2, 1-93), followed by M. salmi (15.7, 1-58) and M. apri (12.6, 3-27). We found a significantly higher prevalence of Metastrongylus spp. and M. salmi in adult wild boars, probably associated with a more prolonged time of exposure to intermediate host species. The phylogenetic analysis revealed that ITS2 region and cox-1 mtDNA are the most suitable genetic markers for Metastrongylus species characterization. Genetic variability between M. apri and M. salmi isolates was verified.

CONCLUSIONS

We expand the knowledge about the Metastrongylus community in the non-captive wild boar population from Brazil as well as the importance of this exotic species in the maintenance of Metastrongylus spp. in its areas of occurrence. The novel genetic sequences obtained may help further studies to understand the genetic diversity in other nematode populations from Brazil and other countries.

Economic losses associated with respiratory and helminth infections in domestic pigs in Lira district, Northern Uganda

This study sought to quantify direct economic losses due to respiratory and gastrointestinal (GI) helminth infections in domestic pigs in Uganda. In a longitudinal study design with repeated measures, farm visits were made at 2 month intervals from October 2018 to September 2019. Weaner and grower pigs (n = 288) aged 2-6  months from 94 farms were sampled. The pigs were monitored for growth and screened for exposure to four important respiratory pathogens: porcine circovirus type 2 (PCV2), porcine reproductive and respiratory syndrome virus (PRRSv), Mycoplasma hyopneumoniae (M. hyo), Actinobacillus pleuropneumoniae (App) using ELISA tests. Farm management practices were recorded and used to generate management level scores. Treatment expenses incurred were recorded throughout the study. A mixed effects model was fitted to quantify effects of respiratory and helminth infections on average daily weight gains (ADGs), with farm and pig as random effects. Analysis of variance (ANOVA) was used to determine differences in mean treatment costs by farm management standard. Financial losses were estimated from average carcass dressing percentage, ADG reductions during fattening (200  days). Results showed a grower pig in a given farm exposed to PRRSv and Ascaris spp. had significantly lower ADG by 17.10 gr/day and 16.80 grams/day respectively, compared to a similar unexposed pig (p < 0.05). Mean treatment costs per pig declined significantly with increase in management standard scores (MSS), from USD 1.13 per pig in MSS 1 (poor management) farms to USD 0.95 for MSS 3 (better management) farms (p < 0.05). We show that monetary losses due to PRRSv and Ascaris spp. infection amounted to USD 6.6 ± 2.7 and 6.50 ± 3.2 (Mean ± SEM) per pig, respectively during 200 days of fattening. This study strengthens evidence that improving management practices to reduce infections mitigates economic losses. To guide interventions, further studies are required to unravel the full extent of indirect economic losses.

Secondary Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus (HP-PRRSV2) Infection Augments Inflammatory Responses, Clinical Outcomes, and Pathogen Load in Glaesserella-parasuis-Infected Piglets

Glaesserella parasuis (Gps), Gram-negative bacteria, are a universal respiratory-disease-causing pathogen in swine that colonize the upper respiratory tract. Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus (HP-PRRSV2HP-PRRSV2) and Gps coinfections are epidemics in China, but little is known about the influence of concurrent coinfection on disease severity and inflammatory responses. Herein, we studied the effects of secondary HP-PRRS infection on clinical symptoms, pathological changes, pathogen load, and inflammatory response of Gps coinfection in the upper respiratory tract of piglets. All coinfected piglets (HP-PRRSV2 + Gps) displayed fever and severe lesions in the lungs, while fever was present in only a few animals with a single infection (HP-PRRSV2 or Gps). Additionally, HP-PRRSV2 and Gps loading in nasal swabs and blood and lung tissue samples was significantly increased in the coinfected group. Necropsy data showed that coinfected piglets suffered from severe lung damage and had significantly higher antibody titers of HP-PRRSV2 or Gps than single-infected piglets. Moreover, the serum and lung concentrations of inflammatory cytokines (TNF-α, IL-1β, IL-6, and IL-8) were also significantly higher in coinfected piglets than in those infected with HP-PRRSV2 or Gps alone. In conclusion, our results show that HP-PRRSV2 promotes the shedding and replication of Gps, and their coinfection in the upper respiratory tract aggravates the clinical symptoms and inflammatory responses, causing lung damage. Therefore, in the unavoidable situation of Gps infection in piglets, necessary measures must be made to prevent and control secondary infection with HP-PRRSV2, which can save huge economic losses to the pork industry.

Molecular characterization of porcine reproductive and respiratory syndrome virus (PRRSv) identified from slaughtered pigs in northern Uganda

Background

A cross sectional study was conducted to detect and characterize species of porcine reproductive and respiratory syndrome virus (PRRSv) identified from slaughtered pigs in Lira district, northern Uganda. The study was conducted from March to September 2019 in three selected slaughter slabs. Pigs brought for slaughter were randomly sampled. At necropsy, lungs were extracted from the thoracic cavity and examined for pneumonic lesions. Seventy-three (73) pigs with gross lung lesions were sampled, from which one hundred and one (101) tissue samples were taken. A real-time reverse transcriptase PCR (RT-qPCR) was used to characterize PRRSv species.

Results

A total of 20 samples tested positive for PRRSv. The respective prevalence of PRRSv type 1 and type 2 were 24.65% (n = 18) and 2.73% (n = 2) respectively. Of the pigs sampled (n = 73), only two pigs, 2.73% (n = 2) tested positive to both species. The likelihood of PRRSv detection decreased with pig age, but increased with gross pneumonic pathology.

Conclusions

This study demonstrated dual circulation of both species in northern Uganda. The association between PRRSv and lung pathology suggests that it may be an important cause of lung disease in pigs in Uganda and hence loss of production. This calls for further investigations on potential economic impacts of PRRSv on pig productivity. These findings contribute to discussions about the need of surveillance and possible vaccination strategies against PRRSv in Uganda.

Lungworms (Metastrongylus spp.) demonstrated in domestic pigs with respiratory disease: was there a clinical relevance?

Background

An outdoor pig herd was affected by severe respiratory disease in one out of three pastures. At necropsy, Mycoplasma hyopneumoniae and Pasteurella multocida were detected in the lungs, as well as the lung worm Metastrongylus apri. The life cycle of Metastrongylus spp. includes earthworms as intermediate hosts, and since domestic pigs mainly are reared indoors, lungworm infections have not been diagnosed in domestic pigs in Sweden for decades, not even in pigs reared outdoors. Therefore, this disease outbreak was scrutinised from the view of validating the impact of Metastrongylus spp.

Results

At the time of the disease outbreak, neither eggs of Metastrongylus spp., Trichuris suis nor Ascaris suum were detected in faeces of pigs aged ten weeks. In contrast, five-months-old pigs at the pasture with respiratory disease shed up to 3800 eggs per gram (Epg) of Ascaris suum and up to 1100 Epg of Trichuris suis, whereas eggs of these parasites were not demonstrated in healthy pigs aged six months at another pasture. Low numbers of eggs from Metastrongylus spp. (< 150 Epg) were seen in faecal samples from both these age categories. At slaughter, seven weeks later, ten normal weighted pigs in the preceding healthy batch were compared with ten normal weighted and five small pigs from the affected batch. Healing Mycoplasma-like pneumonic lesions were seen in all groups. All small pigs shed eggs of Ascaris suum in the faeces, compared to around 50% of the larger pigs. Metastrongylus spp. were demonstrated in 13 of the 25 pigs (52%), representing all groups included.

Conclusion

As Metastrongylus spp. were demonstrated regardless of health status, and also in another healthy outdoor herd, the impact of Metastrongylus spp. on the outbreak of respiratory disease was depreciated. Instead, a possible association with a high burden of Ascaris suum was suggested to have preceded the severe outbreak with respiratory disease in the affected herd. Further, it was concluded that Metastrongylus spp. will escape detection at routine meat inspections made at slaughterhouses, and as they appeared to generally not induce clinical signs of respiratory disease Metastrongylus spp. may be more common in outdoor production than previously believed.

Florfenicol 40% efficacy in piglets with respiratory pathologies

Piglets with large-scale respiratory pathologies caused by a bacterial flora susceptible to phenicol antibacterial drugs received two doses of Florfenicol 40%. On day 4 after administration, this resulted in the complete reversal of clinical pattern, in the recovery of morphofunctional blood parameters, and in the reduction in prevalence of Klebsiella pneumoniae by 25%, Streptococcus suis by 50%, and Staphylococcus haemolyticus by 41.7%. The drug is tolerated with no adverse events. The results of this study allow recommending Florfenicol 40% as an antibacterial therapy in the acute infectious inflammatory respiratory pathologies in the store pigs.