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This edition of IPVS, after the congress in Rio de Janeiro, moved to a new continent. This marks the third time IPVS was hosted in Germany—previously held in Hannover in 1972 for its second edition and in Hamburg in 2004 for its 18th edition. This year's IPVS is taking place alongside the 15th European Symposium on Swine Health Management, following the symposium held a year ago in Thessaloniki, Greece.
The congress chairman was Prof. Dr. Johannes Kauffold who was accompanied by a ten-member organizing committee, an eight-member IPVS steering committee, a seven-member ECPHM steering committee, plus a seven-member committee of German practical veterinarians. The congress was sponsored by 39 national and international companies and partners and there were 45 booths. Some 2,700 delegates from 65 countries attended.
Tom Alexandre Memorial. J. Zimmerman, Iowa State University, Innovation in surveillance
Dr. Tom Alexandre (1930-2008) - "A rare person" - was a professor, researcher, leader, and writer. There is a difference between technical and conceptual innovations. The former fit with what we already believe and do, and act like mouse traps. Conceptual innovations are ideas that change the world, such as those proposed by Tom Aleixandre in 1971: moving to large production units, using genetics with higher production parameters, and creating a vertically integrated industry. He was familiar with a constantly transforming and transitioning swine industry. The average farm size in Canada in 1970 was 66 sows, in 1990 it was 345, and in 2020 it was 902.
As farm size increases, disease ecology changes, making it more difficult to maintain stability. As early as 1987, he said that data is critical for farm management. Producing one kilogram of pigs in 2015 required 76% less land, 25% less water, and 7% less energy compared to 1960. The world pig inventory in 2022 increased 2.9-fold compared to 1961 and pork exports increased 15-fold.
The change the swine industry faces today is the collapse of geographical space and the global spread of pathologies. There are currently 58,288 air routes and the legal trade of pigs between continents and countries is constant (from 1980 to 2023 there has been a 13.9-fold increase in the movement of pigs in the world). Therefore, early disease detection is key to preventing it from spreading and becoming an epidemic problem.
The CSF eradication plan was conducted in the USA from 1961 to 1978, where the average farm size in 1960 was 50 sows and in 1990 it was 200 sows. The technique of routinely detecting antigens in tonsillar cell epithelium on all farms and representative serum samples was sufficient. Sample size according to farm size is a critical factor in accurately determining prevalence, as evidenced by the Aujeszky's disease eradication program in the USA (binomial distribution formula in finite populations and binary result - positive/negative, subjects being dependent on homogeneous populations).
Currently, determining survival at the farm level requires knowledge of regional survival, since the reality must take into account the constant flow of pigs, people, trucks, and products. Therefore, trying to make a single farm negative can mean a high risk of failure, and participation from all farms located in the region is required. A few samples taken from many farms at a time are highly sensitive and reasonably cost-effective.
Virology and viral diseases
African swine fever vaccines: Current situation and perspective. Prof. Hua-Ji Qiu, Harbin Veterinary Research Institute. CAAS, China
The ASF virus is a hot topic in China, causing thousands of deaths. Mortality can reach 100% with acute infections and it has an incubation period of 4-19 days. It is a WOAH notifiable disease with significant social, political, economic, and commercial implications. Vaccines are not approved in Asia except in Vietnam. This virus is the only member of the genus Asfivirus of the Asfarviridae family - DNA. The virus consists of five parts. It was sequenced for the first time in 1995 (BA71v). The virus is 170-194 kb long and encodes 54 structural proteins and 100 non-structural proteins (154 proteins), half of which have unknown functions. Multiple genes are related to its virulence and immunity.
Thousands of outbreaks have been declared between 2022 and 2024, with 1.3 million dead pigs. The virus has found its heaven in China, where different variants have been identified: 2018 Georgia07 high virulence (genotype II), 2020 Georgia07 low virulence (genotype II), 2022 genotype I, and currently both genotypes. Control strategies in China focus on strict biosecurity measures, national, regional, and farm distribution systems, testing and culling in disease outbreaks, and incorporating feed additives to minimize impact.
The different vaccine strategies give variable results since they depend on the virulence of the virus and its homologous, heterologous, and cross-protective capacity. Inactivated vaccines can induce antibodies, but produce very little or no protection, depending on the inactivation systems, adjuvants, and immunization schemes. Subunit vaccines combine baculovirus-expressing proteins or DNA prime-protein strategies. They are safe and DIVA, but produce poor protection. DNA vaccines express plasmid antigens, are safe and DIVA, and induce a strong CTL response and poor protection. Live viral vector vaccines (adenovirus, AdV, vaccinia virus) with eight antigens confer 100% protection but cause viremia and fever. Live attenuated vaccines in which virulence-related genes are deleted and replicate in especific cell lines are safe and effective, provide cross-protection, and are stable. The problem with their development is differentiation from other vaccines. The vaccine candidate in China is HLJ/18-7GD, based on a virulent genotype II strain from which two genes (CD2v and UK) have been deleted, providing good protection and low viremia. His group is developing a cell-adapted ASF virus vaccine candidate.
In Vietnam, vaccines G-/177L and G-AMGF, based on the Georgia 2007 strain developed in the USA, are approved, focusing on deleterious genes, with a reduction of potential risks and knowledge of protection mechanisms.
All vaccines have their advantages and disadvantages. The reasons for not having the ideal vaccine to date are due to a deficiency of basic studies on the biological characteristics of the virus, as well as the multiple transmission cycles of the virus and the mechanisms involved in immune protection, which are poorly understood. At the research level, the limitations of working with highly virulent viruses are restricted by their risk of dissemination. New technologies are needed to identify new vaccine antigens, generate effective replication by deleting essential genes, and regulate in vivo and in vitro research mechanisms. Vaccination is an option, but not the only solution, and biosecurity is essential. Vaccines against ASF will be available in the future and will be used in a restricted way.
Emerging viral diseases: recent global threats. Prof. J. Reis Ciacci Zanella, Embrapa, Brazil
In the last 20 years, many diseases have been transmitted from animals to humans: SARS CoV1, H1N1 influenza virus, MERS, H7N9 avian influenza virus, Ebola, Zika, SARS CoV2, smallpox, and H5N1 avian influenza virus. The emergence and re-emergence of infectious diseases is widespread globally. A pathogen is assumed to be emerging when it appears in the world for four months, 75% being zoonotic and 44% RNA viruses. The main pathogens transmitted via food are not viruses, but bacteria (70%); this varies from continent to continent and is higher in Africa. Pathogens need to be able to infect numerous species to form their emerging zoonotic capacity. Direct contact between humans and animals is an important factor, with up to 31 viruses in common with pigs.
Pigs can be reservoirs, intermediaries, and amplifiers for seven zoonotic viruses and are incidental hosts for 11. People can also infect pigs (SARS, vesicular virus, and norovirus). There is also bidirectional transmission (influenza). Five influenza A virus pandemics have occurred in the last century (1918, 1957, 1968, 1977, and 2009). From 2000 to 2005 the appearance of new virus variants doubled (in swine 86% are new variants) and in 81% of the cases they affect new species. Many emerging pathogens in recent decades have occurred on farms, where they acquire greater virulence until they manifest identifiable clinical signs.
Moving animals across borders causes viruses to travel to different regions, where endemic pathogens change pathogenicity and mode of transmission. Some viruses have significant clinical symptoms and a considerable economic impact (influenza, PCV, PED, PRRS, ASF) and others have unclear clinical presentations and are complex to assess epidemiologically. The demand for pork is a risk factor due to the movement of animals and products involved. Pork accounts for 35% of the protein consumed globally, which is very important for the countries' economies. Production systems are also evolving and condition these risks of dissemination of infectious agents. Genetics, nutrition, and therapeutic guidelines have also changed, which has modified their cardiorespiratory and immune capacity and intestinal ecology. Environmental changes associated with urbanization, with a high concentration of people in cities and the fragmentation of rural areas, together with climate change and water demand are modifying pathogen evolution, causing new mutations and recombinations, and acquiring new virulence factors. Pigs are mammals, abundant, distributed worldwide, in contact with people and wildlife, and have great physiological and immunological similarities with people, which should be considered.
There are several uncontroversial points to reduce emerging diseases: internal and external biosecurity, bio-contaminants, and farm immunity (a poor immune base perpetuates the presence of the virus).
Porcine reproductive and respiratory syndrome (PRRS)
• PRRSV 2 is the predominant virus in the USA and can cause premature farrowing, late abortions, stillbirths, respiratory symptoms, pneumonia, growth loss, and high mortality. Between 30-50% of farms have the active virus. Changes in PRRSV control are due to situations arising from high-density areas, animal movements (vertical integration), and connectivity between regions. Within RNA viruses, the antigenic and genetic diversity of this virus has been very high, with many strains circulating at the same time and new ones emerging. Since 1995, the virus population has increased significantly, combining with lines type 1. Today, it is possible to predict emerging variants using early indicators, allowing their appearance to be anticipated.
• At the University of Minnesota they performed a metadata-based study on 20,500 ORF5 sequences, which account for 55% of those known in the US. A strain map was constructed every six months from 2011-2021, analyzing emerging variants in different populations and geographic areas. They made a prediction model by analyzing early candidate indicators based on the primary structure of the virus, the degree of evolution, and the results of variant strains over time. Variants with more than 15 amino acids changed are 14 times more likely to emerge.
• The main variant of the virus in Europe is type I. In 2020 a highly virulent strain emerged in northwestern Spain with high pathogenicity, coming from a recombinant of Italian and Spanish strains (Rosalia). The in vitro characterization of this strain was done in PAM-KNU cells, identifying the virus in piglets with 25-40% mortality. At 72 hours post-infection they had peak viremia. All strains come from a common ancestor such as the Italian PR40 strain. In two other experimental studies, piglets were infected intramuscularly and intranasally with the Rosalia strain. There was also a control group. They performed necropsies on day 63 and took blood, nasal, and rectal exudates every seven days. Peaks in clinical symptoms were observed at 13 days after infection (fever and average daily growth). 100% mortality in piglets with intramuscular infection occurred on day 14. With intranasal infection, it was 30% at 63 days. All animals were PCR positive at 3 days post-infection in serum, saliva, and nasal and rectal exudates. The virus was found in the IN infection from day 3 to 28 and in the IM group from 3 to 14. IFN alpha levels were elevated from day 3 in all cases. Specific antibodies were detected from day 14 post-infection in both groups. The virus was found by PCR in the organs of infected animals (spleen, liver, lungs, tonsils) with high titers. A high increase of cytokines associated with inflammation was observed in infected animals, especially in the intramuscular group. We must consider iatrogenic transmission important for virus dissemination.
• In the first half of 2020, the first cases of the Rosalia strain appeared in Gerona (Spain), which spread throughout the rest of the country. The impact on breeding sows and piglets is very high, with abortion peaks of 25-30% and weaned piglet mortality of 26% on average, with peaks of 50-60%, impacting Spanish pig production. This study aimed to analyze the efficacy of an intranasal modified live vaccine in 4-week-old piglets subsequently infected with the Rosalia strain five weeks later, with a control group. The vaccination induced seroconversion and IFN gamma in all animals. They observed a reduction in fever in the infected animals that were vaccinated compared to the control, with great variability observed among non-vaccinated individuals. The level of lethargy and respiratory symptoms in vaccinated animals was lower in the vaccinated group than in the control. Regarding pulmonary lesions, interstitial pneumonia was moderate to severe in the non-vaccinated animals and very significantly reduced in the vaccinated animals, with a lower percentage of affected lung at 35 days after infection. The mean daily gain of vaccinated piglets was higher (up to 8 kg difference). Viremia in vaccinated piglets was reduced, being negative at three weeks after infection, and in non-vaccinated piglets it was maintained until day 40, showing a lower virus excretion. Infection with the Rosalia strain results in transient lymphopenia and vaccination helps the secretion of IFN gamma cells.
• There are many options for monitoring populations for PRRS virus on sow farms (tongues, processing fluids, oral fluids, tonsil swabs). PCR-analyzed tongue fluids from stillborn piglets are most sensitive several weeks after clinical symptoms with variations in Ct titers. Oral fluids taken from litters of suckling piglets in the morning, when they are most active, include samples from both the piglets and the mother, and vary 24-94% between all animals. There are doubts about the sample size to be taken (number of litters, piglets per litter), which will undoubtedly give us variable results for prevalence. The same applies to oral fluids in recently weaned piglets, in addition to having to consider the number of piglets, the ages, and the day of sampling. A study by Dr. Marcelo Almeida defines the number of sera and oral fluids to be taken for maximum prevalence. Another issue is determining both the size of each sample pool and the number of pools when determining the dynamics of PRRSV. On the ISU website (www.fieldepi.org/calc) we can find the number of samples according to the estimated prevalence. Monitoring clinical symptoms (anorexia and abortions) and production is useful for early detection, but not for stability. If the sows are positive, we must focus on the time to generate effective immunity. If the sows are negative and the piglets are positive, we must take strict bio-management measures in farrowing crates and check piglets older than 16 days old. If stillbirths are high, does that mean that vertical transmission is active?
• A study from the University of Minnesota evaluated the type and size of samples in finishing pigs to assess PRRSV status. The preferred samples are oral fluids, processing fluids, and environmental samples (airborne particulate emissions). The objective was to determine suitable non-invasive and safe samples for acceptable sensitivity. They aimed to evaluate aerosol emission of PRRSV in 3 wean-to-finish units with about 1,000 pigs per three rooms in 32 barns. Samples were taken between August and February at the outlet of the air extractors for 1.5-2 hours together with oral fluids every two weeks doing individual PCR. Oral fluid samples were always collected from the same pens. Virus detection in both oral fluids and air emissions coincided in time and decayed earlier in oral fluids than in air. The estimated probability of detecting the virus in the air was 4% with 50% positive oral fluids and 40% when 100% positive. The sensitivity of the technique in air emissions decreased as the Cq of oral fluids decreased.
• POMP is a voluntary program run by Iowa State University for veterinarians and producers to manage PRRSV cases. It focuses on diagnostic tests to sequence virus strains associated with strains from PCR testing. They analyze parameters to measure time to stability, time to return to parameters before the outbreak, and the economic impact. Time to PPRSV stability is the number of weeks it takes for weaned piglets to become negative (TTS). The time-to-baseline production (TTBP) is estimated by assessing the production in the 20 weeks prior to the outbreak (total number of piglets weaned weekly). The farm characteristics considered are farm size and some comparative production parameters between farms with varying problems within the study area. They analyzed 176 outbreaks between October 2010 and May 2023 and 87 between 2017 and 2023 with a high incidence in 2023. Farm closure was found to be the most effective. At the end of the study, 85% of the farms carried it out, being the measure that reduced losses the most. Acclimating replacement gilts off-site versus housing them inside the sow farm also reduces the time it takes for the farm to return to stability. The program will include other KPIs such as fertility rate and preweaning mortality to continue improving its predictive accuracy. The virulence of the strains is a determining factor in the intensity of the clinical symptoms and the time required to return to pre-disease production parameters.
• An epidemiological study at Iowa State University assessed the incidence of PRRSV outbreaks. ORF5 represents only 4% of the virus genome. PCRs are based on virus sequencing and differentiate between European and American strains. The NGS (Next Generation Sequencing) technique depends on the sample type (individual lung or sera or pooled oral fluids). It can differentiate whether there are one or more strains in the same sample and can sequence the virus at the same time of the outbreak while knowing the genetic evolution of the virus. The presence of more than one virus strain on the same farm is a reality and results in greater instability. Farms with recombinant strains result in greater economic losses. If more than one strain infects a pig, when they enter the organism both replicate in its cells and give rise to new recombinant strains. There are multiple possibilities for recombination, both between wild and vaccine viruses, and it is feasible to detect recombination using this technique. Introducing replacement sows with a different virus strain from that of the farm facilitates the appearance of more virulent recombinant strains. Live attenuated vaccines are allowed only in healthy animals since administering them to animals infected with the field strain generates recombinant strains. Using two vaccines with different strains on the same farm is discouraged, whether in the breeding stock or between dams and piglets.
• The co-circulation of different strains prevents control measures, including vaccines, from being fully effective. Numerous studies focus on the early identification of emerging viral variants so measures can be taken to mitigate the effects of the disease, carrying out predictive models. They are based on six phylogenetic parameters of variants appearing 12 and 24 months earlier and analyze their spatial distribution and genetic diversity. Both intranasal and intramuscular routes of transmission are important in highly virulent strains. The capacity of virus percolation in slurry, passing to groundwater, is shown to be possible and variable according to the virulence of the strains. Trucks transporting live pigs constitute a high risk of farm contagion. A Danish study found no association between serological results from farms near or far from roads.
• A Hungarian study shows that the swine industry can reduce its carbon footprint by 32% by changing its health status from PRRS positive to PRRS negative, based on the fact that producing one kilogram of pig carcass is equivalent to 6.1 kg CO2, in addition to reducing the use of antibiotics and improving the conversion rate.
• The economic cost of PRRSV in different countries refers to the fact that, over the years, it has either remained the same or increased rather than decreased. In an American study on 1.1 million sows included on 297 farms from 12 different production systems, the production parameters of unaffected farms vs. those that had an outbreak in the last 16 weeks are: born alive per farrowing 13.57 vs. 10.53, litters per sow per year 2.38 vs. 1.98, preweaning mortality 16.57 vs. 33.84%, and sow mortality 10.36 vs. 12.92%.
• In Denmark, a program to reduce the prevalence of PRRS was initiated in 2022, which demands more RT-qPCR testing of processing fluids, tongues, and oral fluids. Correct and hygienic sample collection, storage, and transport are critical to avoid detecting false negatives. They recommend storing serum at 4ºC, oral fluids at -20ºC, and processing fluids at -80ºC. Storage at room temperature for one day results in a significant increase in the Cq value of all samples and severe difficulty in detecting the virus.
• In the USA, relapses of PRRS on the same farm are frequent due to different viruses of similar sequences (re-break), which suggests that the virus has changed. In these cases, the previous farm's homologous immunity is not enough to avoid clinical disease. This makes us suspect the virus can evade the animals' immunity.
• Next-generation sequencing (NGS) technology reveals, in many cases, the coexistence of wild-type and vaccine virus strains in the same samples.
• Numerous studies highlight that piglet mortality is reduced by administering different vaccines at different times - days of life of the piglets (3 days to 3 weeks old). In the same sense, the use of vaccines in breeding sows to reduce the impact of the virus on production parameters is also the subject of several posters.
African swine fever (ASF)
• Practical Emergency management of ASF, Romania – Dr. A. Balaban. In April 2020 they had the first case of ASF on a farm, which started with two dead sows on the same day and six others with high fever, along with some abortions. In addition, there were sows with anorexia while the rest of the sows were normal. The necropsied animals had typical lesions: petechiae in the kidneys, hepatomegaly, and hemorrhages in different organs. The first laboratory diagnosis was negative. The affected farms were culled and all farm movements in the area were limited. Subsequently, biosecurity programs were implemented with strict hygiene and disinfection measures, both for farms and transport vehicles and areas around the farms, creating restrictive areas for movements of both animals and people.
• The actual individual risk index does not only exist as a scientific definition since not all specific factors are measurable. Biosecurity is the central pillar of prevention against ASF, which is of particular interest at the moment due to the spread of the virus in part of Europe and the increase of pigs in open production systems that have access to the exterior.. In March 2023, a project started in Germany that is fully funded by the state of Hessen with the support of the Ministry of Agriculture. It has a panel of 39 experts and an epidemiological Delphi study to identify risk factors. The 39 biosecurity experts are divided into three groups: some identify, others assess the weight of the factors (first they separate issues, descriptive and statistical status), which add up to 113 risk factors. Within these, there are three categories: farm location (50), daily management of routine farm work (46), and general hygiene measures (17). Each risk factor is assigned a weight. Specific factors for contact with people and wild boar are farm location, farm structure, number of pigs, farm personnel, walking areas - hunting, and feeding and bedding materials. www.risikoampel.uni-vechta.de Within a few minutes, the risk assessment program ranks individual risks in decreasing order. Some of the main risk factors are management and feed in extensive farms with few animals.
• After an outbreak, mortality varies. Persistent infection results in carrier pigs and transplacental infections, contributing to virus circulation on the farm. Antibodies may remain up to six months later.
• Incorporating immune system stimulant complexes such as glycerol monolaurate in feed for pigs infected with ASF virus reduces the severity of the clinical symptoms.
• Semen is an important factor in virus transmission to consider, so control in boar studs is critical.
• The French Anses group is developing an experimental vaccine candidate with the ASFV-989 strain proven to be safe and effective both intramuscularly and intranasally. The next step is to develop the vaccine by adapting the strain to porcine alveolar macrophages in a continuous cell line. Further studies are needed to evaluate its stability and increased intramuscular efficacy after the good results with the gold nasal route.
Influenza
• Numerous studies describe the epidemiology and evolution of the influenza virus circulating in their countries in both humans and swine. For example, in the Netherlands, the influenza A virus is detected in 77.8% of farms in all seasons of the year, with 129 different sequences, with H1N1 prevailing, followed by H1N2 and H3N2. The greatest diversity is found in H1, while identifying different viruses on the same farm simultaneously, detecting transmission between humans and pigs. Eighty-five percent of positive farms report clinical signs in suckling and weaned piglets.
• Samples from oral fluids reduce the cost and increase the probability of virus detection.
• The highly pathogenic H5N1 avian influenza virus continues to infect chickens, wild birds, and mammals throughout the world. In mammalian infections, the strains adapt through mutations, replicating in the upper respiratory tract, increasing the risk of infection and establishing itself as an endemic virus in swine.
• In experimental trials infecting piglets with H1N2 and incorporating a Bacillus subtilis and B. licheriformis-based probiotic in the sow feed five weeks before farrowing and in the piglets three weeks after weaning, piglets from treated dams and piglets eating the probiotic had lower fever, respiratory index, and better feed efficiency than controls.
• The diversity of the hemagglutinin (HA) of the influenza A virus poses a major challenge for vaccine development. Matrix protein 2 (M2) is a highly conserved envelope protein and more than 98% of influenza virus strains circulating in US swine farms have an identical pandemic isoform of M2. It is a tetrameric protein with 97 amino acids. At the University of Illinois Urbana, they are developing an experimental vaccine with this protein on a soluble nanoscale structure called nanodiscs (NDs). They vaccinate 5- and 9-week-old piglets both intranasally and intramuscularly, obtaining strong protection, offering a promising possibility for the development of universal vaccines against the influenza virus.
• Influenza A virus infections in breeding sows can cause decreased conception rates, low piglet viability, low birth weights, and early farrowing, which, in some studies, is resolved by vaccinating breeding sows.
• Co-infections with influenza viruses are frequent within the swine respiratory complex, the most frequent being with PCV2 (0-31%), PCV3 (5-38%), Actinobacillus pleuropneumoniae (0-42%), Glaeserella parasuis (69-100%), Streptococcus suis (96-100%), Bordetella bronchiseptica (0-61%), Mycoplasma hyorhinis (55-89%), Pasteurella multocida (31-62%), with large variations between countries and production systems. In some estimates, respiratory pathologies in finishing pigs cause losses of up to $10/pig.
Porcine circovirus (PCV)
• Porcine dermatitis and nephropathy syndrome (PDNS) is a pathological clinical presentation whose diagnosis is histologically characterized by a necrotizing vasculitis and fibrinonecrotic glomerulitis, included within swine circovirosis in the current epidemiological circumstances, after the reduction of its prevalence by the use of vaccines against PCV2. PCV3 and PCV4 have also been detected in PDNS. PCV is ubiquitous and is not always linked to disease, with PCV2 being the most associated with PDNS. Porcine embryos are susceptible to PCV2 infections, causing embryonic deaths, stillbirths, and mummified embryos.
• PCV4 has been isolated in the USA and Spain for the first time and has been detected in wild boar.
• Several studies refer to the reproductive problems derived from PCV that are well resolved with vaccination in sows and replacement sows, to reduce the risk of excretion and transmission to piglets during lactation.
Other viruses
• Viral coinfections are common on swine farms, aggravating infectious processes and causing serious economic losses. Identifying all viruses and their variants at the same time is very difficult with current diagnostic techniques. At the University of Minnesota they have developed the "TELSVirus" (Target-Enriched Long-read Sequencing of Virus) concept, which is capable of detecting and genomically characterizing multiple viruses in real time (24 hours) and discriminating their variants from simple samples (oral fluids). Other studies provide data in the same vein, using the random method of nanopore sequencing. In healthy farms they find up to 22 virus species in stool samples, nasal swabs, which shows that the sensitivity of current PCR techniques varies depending on the type of virus. We must always keep in mind the principle that infection is not the same as disease.
• Porcine epidemic diarrhea virus (Coronavirus) was first identified in the USA in April 2013, having an epidemic period of 1.5 years, with a transition to an endemic one. They analyzed 1,028 farms between May 2013 and June 2023, of which 236 had an epidemic outbreak and 230 an endemic one. The mean time they were positive was 25 and 17 weeks in epidemic and endemic farms, respectively. The mean time to return to normal was 24 and 14 weeks in epidemic and endemic farms, respectively. The use of feedback practices, inoculating with intestinal macerates from piglets with diarrhea to generate maternal immunity, showed that viral titer and virulence were negatively correlated with increased passages, both in vivo and in vitro, causing genetic alterations and accelerating the degree of genetic change.
Parasitology
• The incidence of white spots in the livers of slaughter pigs is the consequence of the ingestion of infected eggs or larvae of Ascaris suum, and its prevalence continues in different countries where the use of antiparasitics is suppressed in both sows and piglets. If the larvae migrate to the lungs, this predisposes the pig to other respiratory infections.
• The incidence of Cystoisospora suis (Coccidiosis) in suckling piglets (100 to 50,000 oocysts/gram feces) is recurrent on farms, so different toltrazuril-based products, with or without iron, intramuscular or oral, are administered in the first days of life, with positive effects, observing some differences in the average daily gain of piglets between products (10-20 g/day). Its diagnosis can be made by flotation in feces, autofluorescent microscopy, and currently by real-time PCR (Cocci Screen - Ceva) quantitatively (Ct <30 highly positive and >38 negative). In Denmark, they estimate a prevalence between 56-66%, and in France 65-70%.
Antonio Palomo Yagüe
