Emerging diseases in swine

PRESENTATION

BROCHURE

EMERGING DISEASES IN SWINE

Margarita Martín, Joaquim Segalés, Laila Darwich, Enric Mateu and Jordi Casal

Emerging diseases in swine

Emerging and reemerging diseases require a rapid and effective response from veterinary professionals and health authorities, in terms of both their identification and containment, in order to minimise morbidity and mortality rates in the affected population and limit their spread. This book, written by experts with a wide experience in the field, reviews, in a practical and concise manner, the emerging and reemerging diseases of swine of economic or zoonotic importance, as well as those with an impact that is still to be determined, but against which active and efficient epidemiological surveillance is necessary.

EMERGING DISEASES IN SWINE

Margarita Martín, Joaquim Segalés, Laila Darwich, Enric Mateu and Jordi Casal

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✱ Production animal vets. Swine ✱ Animal production technicians ✱ Veterinary students FORMAT: 11 × 20 cm.

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Authors MARGARITA MARTÍN Assistant Professor at the Faculty of Veterinary Medicine of the Universidad Autónoma de Barcelona (UAB). Researcher at the Centre for Research into Animal Health (CReSA).

JOAQUIM SEGALÉS Director of the CReSA and an Assistant Professor at the Faculty of Veterinary Medicine of the UAB.

LAILA DARWICH Associate Professor at the Department of Animal

Health and Anatomy of the UAB and she is also a researcher at the CReSA.

ENRIC MATEU Assistant Professor of infectious diseases at the Faculty of Veterinary Medicine of the UAB and a researcher at the CReSA.

JORDI CASAL Professor at the Faculty of Veterinary Medicine of the UAB and researcher at the IRTA/CReSA.

KEY FEATURES:

➜ Practical approach to emerging and reemerging diseases of swine with an economic impact on the pig industry. ➜ Written by renowned specialists in this topic. ➜ Specific chapter about other infections of swine with an impact that is still to be determined.

Emerging diseases in swine

Presentation of the book In the past few years, we have become accustomed to news about new diseases, the reemergence of others that were already known but are now caused by new strains, or about infections that no longer respond to the usual drug treatments and against which there is no rapid and effective alternative.

All of them are encompassed in the concept of emerging and reemerging diseases, which pose, for us veterinary professionals, new challenges in terms of how to diagnose and treat the affected animals. The control of the spread of these diseases within a region and to other areas is another challenge that must be addressed to minimise their impact on animal health and production, as well as on global trade. In the case of infections caused by agents that are also pathogens of humans (zoonoses), adequate surveillance and control of the animals is of paramount importance, even when the effects of these pathogens may be of little significance or may even go unnoticed.

This book describes, in a practical and concise manner, the emerging and reemerging diseases of swine with an economic impact on the pig industry and which, on many occasions, lack effective control methods. We have also included zoonotic infections of swine that may be transmitted by direct contact, through the consumption of meat products, or by other routes. In the past few years, these zoonoses have raised great interest in public health due to the role animals can play in their maintenance and transmission to humans.

Finally, we have dedicated a chapter to other infections of swine with an impact that is still to be determined, but against which we must be vigilant from an epidemiological and diagnostic point of view.

The authors

The authors Margarita Martín PhD in Veterinary Medicine, Dipl. ECPHM She graduated in veterinary medicine from the University of Zaragoza in 1984 and obtained her PhD in veterinary medicine from the Autonomous University of Barcelona (UAB) in 1992, for her work on the epidemiology of coronavirus infections in pigs. Since 1993, she has been professor at the Faculty of Veterinary Medicine of the UAB, where she teaches about infectious diseases in swine, birds and carnivores. She is also a researcher at the Centre for Research into Animal Health (CReSA). She has been a research fellow at the University of Minnesota and Virginia Tech (United States), where her work focused on the diagnosis of swine viral diseases, such as PRRS and hepatitis E. In 2009 she became a diplomate of the European College of Porcine Health and Management (ECPHIM). Most of her research has been focused on the study of bacterial and viral infections in swine, and she has participated in many competitively funded and contract-based research projects, and research papers.

Joaquim Segalés PhD in Veterinary Medicine, Dipl. ECVP, Dipl. ECPHM He graduated in veterinary medicine from the Autonomous University of Barcelona (UAB) in 1991 and earned his PhD from the same university in 1996. He spent 15 months at the University of Minnesota researching for his PhD. In the year 2000, he became a diplomate of the European College of Veterinary Pathologists (ECVP), and he is a founder member of the European College of Porcine Health and Management (ECPHM). He is currently the director of the Centre for Research into Animal Health (CReSA) and a professor at the Faculty of Veterinary Medicine of the UAB (main subjects: pathology and swine medicine).

He has worked as a specialist in diagnosis at the Pathology Department of the Faculty of Veterinary Medicine (UAB) since 1993. He has also been the head of the Swine Diagnostic Pathology Service (1996–2012). Since 1996 his research has focused on swine diseases, and more particularly on infectious diseases (infections caused by the porcine reproductive and respiratory syndrome virus [PRRSv], Aujesky’s disease virus, porcine circovirus type 2 [PCV2], virus of porcine hepatitis E, Torque teno sus virus [TTSuV], Haemophilus parasuis and Mycoplasma hyopneumoniae). He is the coauthor of more than 200 papers in scientific in peer-reviewed journals.

Emerging diseases in swine

Laila Darwich Master’s degree and PhD in Veterinary Medicine She graduated in veterinary medicine from the Autonomous University of Barcelona (UAB) in 1999. In 2001 she completed a master’s degree in veterinary medicine (UAB) and earned her PhD in veterinary medicine in 2004. She was a postdoctoral researcher (2005-2007) at the HIV Unit of the IRSICaixa Foundation (AIDS Research Institute, Germans Trias i Pujol Teaching Hospital, Badalona). She is currently professor at the Department of Animal Health and Anatomy of the UAB and she is also a researcher at the Centre for Research into Animal Health (CReSA). She has been a research fellow at the Roslin Institute (University of Edinburgh). She is the coordinator of the Master’s Degree in Zoonosis and One Health of the UAB and co-coordinator of the Erasmus Mundus Joint Masters’ Degree in Infectious Diseases and One Health, organised by the universities of Tours-France, UAB and Edinburgh. Her areas of specialisation are immunity, immunopathology and epidemiology of viral pathogens of pigs (PCV2, PRRSv) and humans (HIV, HPV), and zoonotic agents in pigs and wild animals.

Enric Mateu PhD in Veterinary Medicine, Dipl. ECPHM He graduated and earned his PhD in veterinary medicine from the Autonomous University of Barcelona (UAB) in 1989 and 1993, respectively. He is currently professor of infectious diseases at the Faculty of Veterinary Medicine of the UAB and a researcher at the Centre for Research into Animal Health (CReSA). He was a research fellow at the University of Illinois (USA) in 1994–1995. His research is focused on swine medicine, more particularly viral diseases. He has participated in several projects related to porcine circovirus, swine influenza and PRRS, among other pig diseases, and he is the author of more than a hundred papers published in international journals. In 2009 he became a diplomate of the European College of Porcine Health and Management (ECPHM). His current research focuses on the control of infectious diseases in pigs, mainly PRRS and swine influenza.

Jordi Casal PhD in Veterinary Medicine, Dipl. ECVPH He graduated in veterinary medicine from the University of Zaragoza in 1979 and obtained his PhD in veterinary medicine from the Autonomous University of Barcelona (UAB) in 1988. He has been professor at the Faculty of Veterinary Medicine of the UAB since 1984 and researcher at the IRTA/CReSA since 2001. He mainly teaches the subjects of Epidemiology and Public Health Policy. He was the general coordinator of the Master’s Degree in Swine Pathology and Production of the UAB (1992–1998) and subdirector of the Interuniversity Master’s Degree in Swine Health and Production (2005–2014). He became a diplomate of the European College of Veterinary Public Health (ECVPH) in 2001. He has published about 80 research papers, mainly on epidemiology.

Table of contents 1. Introduction Definition and importance of emerging diseases Factors that influence emergence Control of emerging diseases

2. Diseases with an impact on production Porcine reproductive and respiratory syndrome Porcine circovirus type 2 and associated diseases African swine fever Porcine epidemic diarrhoea/New porcine coronavirus Rotavirus infection Vesicular disease associated with senecavirus A Infection with atypical porcine pestivirus

3. Diseases of zoonotic importance Swine influenza Nipah virus infection Hepatitis E Clostridium difficile infection Cysticercosis Japanese encephalitis Infections by multidrug resistant bacteria n Streptococcus suis infection

4. Novel infections with an undefined impact Bocavirus infection Torque teno sus virus infection Porcine circovirus type 3 infection

5. Bibliography

Editorial Servet

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+34 976 461 480

EMERGING DISEASES IN SWINE

Margarita Martín, Joaquim Segalés, Laila Darwich, Enric Mateu and Jordi Casal

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Diarrhoea, dehydration and vomiting. Also isolated from healthy animals. Possible coinfection with other viruses to produce clinical signs

Enteritis with some strains. Reproductive failure and pneumonia have been described in infected pigs

Diarrhoea, vomiting and diarrhoea. Subclinical Subclinical. Diarrhoea in co-infections with enteric pathogens

Pigs (humans and possible recombination with human strains)/Asia, Europe, Africa, North America/Unknown transmission, detected in faeces, oral fluids, serum and tissues Pigs/Asia, Europe, Africa and Brazil/ Faecal–oral. Wild boar are carriers and a possible source of infection to domestic pigs

Wide variety of hosts, although speciesspecific. Possible zoonosis, although no human infection has been documented from MRV of pigs/Ubiquitous/Faecal–oral, respiratory secretions, foetuses Pigs/Worldwide/ Faecal–oral. Possible zoonosis l Worldwide/Pigs/ Faecal–oral. Possible zoonosis. Adult carrier animals

Porcine bocavirus Parvoviridae PBoV/ 7 genotypes with 3 subgroups: PBoVG1, G2, and G3

Porcine kobuvirus Picornaviridae/PKoV/Subtype Aichivirus C (PKoV/AiV-C) exclusive to pigs

Mammalian orthoreovirus Reoviridae/MRV/5 serotypes; MRV1-3 is detected in pigs

Porcine sapovirus Caliciviridae/PSaV/Speciesspecific genotypes

Direct: RT-PCR Serology: ELISA

Direct: RT-PCR, IF, IHC, ELISA Serology: ELISA

Direct: culture, IF, ID, RT-PCR Serology: SN, IHA

Direct: RT-PCR, ELISA Serology: SN for human kobuvirus

Direct: culture, IF, PCR, ELISA Serology: ELISA

Direct: RT-PCR, antigen detection by IF, IHC Serology: ELISA, SN

Direct: culture, antigen detection by IF, ID Serology: IF, SN

Diagnosis

ELISA, enzyme-linked immunosorbent assay; ID, immunodiffusion; IF, immunofluorescence; IHA, inhibition of haemagglutination; IHC, immunohistochemistry; PCV-2, porcine circovirus type 2; PMWS, postweaning multisystemic wasting syndrome; RT-PCR, reverse transcription-polymerase chain reaction; SN, seroneutralisation.

Porcine torovirus Coronaviridae/ToV

Mild diarrhoea in piglets. Neurological signs associated with PAstV: leg weakness, paraplegia, seizures. Possible association with congenital tremor

Pigs (suspected in people)/Worldwide/ Common coinfections with other enteric pathogens (rotavirus, coronavirus, PCV-2)/ Faecal–oral

Porcine astrovirus Astroviridae/PAstV/High genetic variability Subclinical. Coinfections common, associated with PMWS, respiratory signs and diarrhoea

Subclinical. It can cause enteritis, encephalitis, nephritis, respiratory disease, reproductive disorders

Clinical presentation

Pig/Worldwide/Faecal–oral, inhalation

Epidemiology (Main host/Geographical distribution/ Transmission)

Porcine adenovirus Adenoviridae/PAdV/3 species (A-C) and 5 serotypes (1–5): PAdV-A (1–3), PAdV-B and PAdV-C

Aetiology (Family / acronym / species and/or types)

Table 1. List in alphabetical order of other viruses detected in cases of piglet diarrhoea, whose importance is still to be defined.

EMERGING DISEASES IN SWINE 2 Diseases with an impact on production

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VESICULAR DISEASE ASSOCIATED WITH SENECAVIRUS A

Based on these findings, many researchers have suggested that the disease previously called porcine idiopathic vesicular disease

BACKGROUND, GEOGRAPHICAL DISTRIBUTION AND DISSEMINATION FACTORS Senecavirus A (SVA), previously known as Seneca Valley Virus (SVV001), was found incidentally in 2002 when an adenovirus-based vector was grown on the PER.C6 cell line. The virus is named after a state park near the location of the laboratory that discovered it (Seneca Creek State Park, Maryland, United States). At the time, it was speculated that the virus had most likely been inadvertently

(PIVD), described in the 1980s–2000s in North America, Europe and Oceania, was probably caused by infection with SVA. Currently, the vesicular disease associated with SVA has also been described in Canada, Colombia, Thailand and China. It is unknown how far it has spread worldwide. There is only one retrospective serological study related to SVA in Brazil. Interestingly, antibodies against the virus were detected the same year that the disease was described for the first time (2014), but not before. This would suggest that SVA was introduced into Brazil around that time, but the origin and mode of introduction are unknown.

introduced into the cell culture by the addition of trypsin of porcine origin. The existence of a serological relation to some previously isoesis of porcine origin.

CLINICAL SIGNS OF EMERGING DISEASE

The discovery of this virus as a contaminant of cell cultures led to

The vesicular disease associated with SVA is clinically very similar to

another curious finding; SVV-001 could cause cytotoxicity in cancer

other swine vesicular diseases. Adult sows and finishers are particu-

cells without causing significant damage to healthy cells. This is why,

larly affected, although it is also occasionally seen in younger animals.

initially, it was considered a potential oncolytic agent, especially of

Vesicular lesions can be preceded by a low-grade fever (40–41 °C)

neuroendocrine and pulmonary tumours in humans. However, cancer

and anorexia. The morbidity of this disease tends to vary according

patients treated with this virus were found to develop neutralising anti-

to the age group, ranging from 0.5–5 % in weaners to 5–30 % in fin-

bodies against it, which limited its usefulness as an oncolytic agent.

ishers. The highest prevalence tends to occur in adult sows, in which

lated porcine viruses in the United States strengthened the hypoth-

Generally, SVA was considered nonpathogenic for pigs. In 2014– 2015, Brazil and the United States reported almost simultaneously

it may reach 70–90 %. In all cases, mortality in these age groups is very low (<0.2 %).

that this virus was associated with signs of a vesicular disease in

Vesicles are usually visible some 3–4 days postinfection, especially

pigs that was very similar to other vesicular diseases such as foot-

on the feet, more specifically on the coronary bands and in the inter-

and-mouth disease. In particular, the presence of vesicles on the

digital areas. These vesicles burst very quickly, but more vesicles

snout and on the coronary band of the hooves in adult sows and

may appear in initially unaffected areas, also on the feet, and later

finishers was described, as well as an increase in neonatal mortality

around the mouth and on the snout (Fig. 1). Generally, no more

during the first week of life. It has been possible to reproduce the

vesicles appear after day 10 postinfection. The rapid rupture of the

vesicular disease in 9-week-old pigs, which confirmed the aetiology;

vesicles is accompanied by erosion and occasionally, ulceration and

however, not all experimental infections have been able to reproduce

necrosis of the affected areas (Fig. 2).

the clinical signs. It is probably a multifactorial disease that only in some concrete cases leads to signs of vesicular disease.

The foot lesions are often associated with more or less obvious signs of lameness. In some cases, the pain can cause the animals to rest

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EMERGING DISEASES IN SWINE

nificant macroscopic or microscopic lesions are found at necropsy, aside from oedema of the mesocolon and catarrhal enteritis in some cases. Neonatal mortality tends to precede the appearance of vesicles in sows and finishers, although the two presentations do not necessarily coincide on the same farm. Cases have been described of SVA infections with neonatal mortality without the coexistence of vesicular disease, and vice versa.

DIFFERENTIAL DIAGNOSIS The differential diagnosis of SVA infection, in particular of its vesicFigure 1. Vesicle on the snout of a sow infected with SVA. Image courtesy of Dr David Barcellos (Federal University of Rio Grande do Sul/UFRGS, Porto Alegre, Brazil).

ular form, is summarised in Table 1. It is very difficult to establish a differential diagnosis in cases of neonatal mortality, since there is a multitude of infectious and noninfectious processes that can cause mortality in the first week of life.

Neonatal mortality is so nonspecific that it is very difficult to establish a differential diagnosis.

Figure 2. Necrosis of the coronary band in a piglet infected with SVA. Image courtesy of Dr David Barcellos (Federal University of Rio Grande do Sul/UFRGS, Porto Alegre, Brazil).

their weight on the carpal or tarsal joints, causing erosions on these

AETIOLOGICAL DIAGNOSIS: LABORATORY TECHNIQUES AND THEIR INTERPRETATION Diagnostic techniques for SVA infection are relatively little developed and are only available in some countries, generally those where the infection has been described.

areas that are not associated with the viral infection (abrasion caused

Different techniques based on the reverse transcription polymerase

by contact with the ground).

chain reaction (RT-PCR) have been developed for the detection of

In addition to vesicular disease, SVA has been associated with a high mortality rate (up to 70 %) in piglets in the first week of life (1–5 days of life). This increase in neonatal mortality is transitory, lasting approximately 1–2 weeks. Affected piglets show emaciation, lack of vigour, diarrhoea and/or sudden death. Interestingly, no sig-

SVA RNA. There are both conventional RT-PCR (offering a positive or negative result) and quantitative RT-PCR tests. Vesicular fluid is the sample with the highest amount of virus. However, as the vesicles burst easily it is not always easy to obtain this material. The virus can also be detected in serum, tonsils, faeces and oral fluid, but

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EMERGING DISEASES IN SWINE

samples should be taken from acutely infected pigs, as the virus is usually rapidly eliminated from the body (between 5â&#x20AC;&#x201C;10 days).

This correlates with the detection of antibodies, since seroconversion tends to be rapid (IgM is detected from day 5 after infection

CURRENT APPROACH TO CONTROL AND PREVENTION

and by day 21 there is already a high amount of circulating IgG).

Currently there is no method of control or prevention for SVA infec-

Currently, there are tests for the detection of antibodies (enzyme-

tion. In all cases, evidence of a vesicular disease must be reported

linked immunosorbent assay [ELISA], indirect immunofluorescence

immediately to the competent veterinary authorities and an extensive

and virus neutralisation).

differential diagnosis must be carried out to exclude other vesicular

A very limited number of laboratories have developed immunohistochemistry (IHC) and in situ hybridisation (ISH) on tissue fixed in formalin and embedded in paraffin. However, these techniques are almost exclusively used in research. Histopathology is not very

diseases, especially foot-and-mouth disease. When SVA infection is confirmed, general disinfection and both internal and external biosecurity measures are thought to help prevent the spread of the virus.

specific for the diagnosis of SVA infection, although it may be useful to select samples for IHC or ISH. Table 1. Main differential diagnoses of infection with SVA. Disease Infection associated with Senecavirus A (SVA) Foot-andmouth disease

Virus

Distribution of vesicular lesions

Susceptible species

SVA (Senecavirus of the Picornaviridae family)

Snout, oral mucosa, coronary band, interdigital area

Pigs

FMD virus (aphthovirus of the Picornaviridae family)

Snout, oral mucosa, Cloven-hooved tongue, pharynx, animals (mainly pigs coronary band, and ruminants) interdigital area, teats

SVD virus Swine (enterovirus of the vesicular Picornaviridae disease (SVD) family)

Snout, oral mucosa, tongue, coronary band, hooves, heels

Pigs

VS virus (vesiculovirus of the Rabdoviridae family)

Snout, oral mucosa, tongue, coronary band, interdigital area, heels, teats

Pigs, cattle, horses

SVE virus (vesivirus of the Caliciviridae family)

Snout, oral mucosa, coronary band, interdigital area, heels

Pigs, pinnipeds (seals, sea lions, walruses, etc.)

Vesicular stomatitis (VS) Swine vesicular exanthema (SVE)

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INFECTION WITH ATYPICAL PORCINE PESTIVIRUS

BACKGROUND, GEOGRAPHICAL DISTRIBUTION AND DISSEMINATION FACTORS Pigs are susceptible to different species of the Pestivirus genus

affected by CT and that was positive for APPV by reverse transcrip-

(Flaviviridae family). Traditionally, classical swine fever virus (CSFV),

tion-polymerase chain reaction (RT-PCR). Nearly all piglets that were

bovine viral diarrhoea viruses (BVDV-1 and BVDV-2) and border dis-

born to these sows developed CT. At the same time, a Dutch research

ease virus (BDV) formed the group of pestiviruses capable of infect-

group was also able to reproduce CT type AII in piglets after intramus-

ing suidae. While CSFV is the causative agent of a notifiable disease

cular injection of serum that was RT-PCR positive to APPV in sows on

according to the World Organisation for Animal Health (OIE), due

day 32 of gestation.

to its transmissibility and the significant economic losses it causes worldwide, BVDV and BDV generally cause subclinical infection in the pig (only occasionally have they been related to mild disease).

Both studies made it possible to establish a relatively clear association between CT type AII and foetal infection with APPV.

A few years ago, a new member of this genus was described in

Subsequently, APPV has been the subject of studies in multiple coun-

Australia: the Bungowannah virus, associated with reproductive

tries, and an association with CT type AII has been confirmed wher-

disease and myocarditis. More recently, in 2015, a new pestivirus,

ever it has been studied. It is now known that APPV is disseminated

markedly different from those previously described, was detected by

worldwide, with an estimated prevalence of seropositive animals

metagenomics. This new agent was called atypical porcine pesti-

of approximately 60Â % (average percentage in animals of different

virus (APPV).

ages and different countries and continents), which would suggest

Interestingly, APPV was detected in samples of a massive sequencing project of the porcine reproductive and respiratory syndrome virus (PRRSV) in the United States. It was therefore unknown if it was related to any specific disease or clinical signs. Moreover, this study confirmed that the positive samples belonged to pigs from different states, so it was postulated that the virus could be widely disseminated throughout the country. Shortly afterwards, in 2016, also in the

that subclinical infection is probably the most common expression of this virus. On the other hand, phylogenetic studies show a high variability of APPV sequences, both between distant geographical areas and within the same country and even within the same farm.

It is also known that APPV can be present in semen. However, it is unknown what role it plays in venereal transmission, foetal infection or the possible development of CT in the litter of the infected sow.

United States, another metagenomic study carried out on samples of

A recent retrospective study conducted in Spain showed that APPV is

piglets affected by congenital tremor (CT) type AII, found sequences

not a new virus, and was already present in pig herds in 1997. Taking

very similar to APPV. In this study, the researchers went further and

into account that CT type AII has been known for almost 100 years,

inoculated foetuses of sows on days 45 and 62 of gestation (via

it is very likely that the APPV, although recently discovered, has been

the amniotic sac); the inoculum consisted of serum from an animal

circulating in domestic pigs over a long period of time.

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CLINICAL SIGNS OF EMERGING DISEASE Based on the available serology and virus detection data, subclinical infection is the most common form of APPV. Although it is still too early to know all the epidemiological and pathogenic characteristics of APPV, it is known to cause persistent infections. However, it is still unknown if persistently infected animals show any clinical condition caused by APPV during their lifetime.

The clinical disease associated with APPV is basically CT type AII. CT is characterised by a delay in the development of myelination of the central nervous system (CNS). This is why, at birth, affected animals present with constant tremor (congenital myoclonus) that tends to disappear with age. This generalised tremor is most apparent in

Figure 1. Cerebellum of a pig affected by CT type AII. Note the presence of neuropil vacuolisation of the white matter of the cerebellum (hypomyelination). This lesion is usually observed in different types of CT type A.

the head and limbs, especially when the animal is standing. At rest, the tremor is less evident. In the most serious cases, the tremor can last until 4â&#x20AC;&#x201C;8 weeks of age, occasionally even longer. The number

DIFFERENTIAL DIAGNOSIS

of clinically affected animals within a litter is variable, ranging from a

CT is a disease that is easy to diagnose clinically. A diagnosis of CT

few piglets to the entire litter. Mortality tends to be low, as long as the

is almost unequivocal in piglets with generalised tremor (especially

tremor does not prevent the animal from taking colostrum and milk.

of the head and limbs, less when the animal is at rest). Neverthe-

If they are unable to suckle, affected animals die from starvation.

less, there are multiple causes of CT, which is differentiated into types

The tremor disappears once CNS myelination is completed. Histologically, the hypomyelination is visible as vacuolisation of the neuropil of the CNS, especially in the white matter of the cerebellum (Fig. 1).

A and B. Type A is characterised by evidence of histopathological lesions of hypomyelination of the CNS, while type B is not. The different causes of CT known today and its clinical and epidemiological characteristics are summarised in Table 1. CT type AII is considered to be the most common worldwide.

CT type AII tends to be more frequent in piglets from gilts, which is why the most severe cases tend to occur on newly established farms. This was one of the traditional arguments suggesting that CT type AII was of viral origin (indicative of inducing immunity in the breeding stock). There is no predisposition for sex or breed (unlike other types of CT). The clinical and epidemiological characteristics of CT type AII are summarised in Table 1.

AETIOLOGICAL DIAGNOSIS: LABORATORY TESTS AND THEIR INTERPRETATION The diagnosis of APPV infection is very underdeveloped and is rarely available at conventional diagnostic laboratories. Different techniques based on RT-PCR for the detection of APPV RNA have been developed.

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Variable

Variable

No

Both

Variable

Variable

Variable

Unknown

B

RT-PCR techniques can either be conventional (offering a positive or negative result) or quantitative.

The virus causes a systemic infection, and can be found in multiple

Yes

<1 month

lymphoid organs, kidneys, and the heart. The viral load can vary according to the organ, although a large amount of APPV genome is

Yes

Indefinite

usually found in whole blood, the CNS and lymphoid organs. There are very few studies currently monitoring the infection by this virus, but preliminary data suggest that it can cause persistence in the host, which is characteristic of pestiviruses.

Yes

In a very limited way and for the purposes of research, a serologIndefinite

No British Saddleback Landrace

High

Both Both

High High

Males

High

>90 % ≈25 %

Low Low

≈25 %

RNA of the virus has been detected in the cerebrospinal fluid, CNS,

ical technique based on an enzyme-linked immunosorbent assay (ELISA) has been developed for the detection of specific antibodies against the Erns protein of APPV. This technique has shown a rela-

No

<4 months

No

Low

Both

High

tively high seroprevalence in all the countries studied (mainly Europe Variable, up to 100 %

APPV

AV AIV

Genetics; autosomal recessive gene Genetics; recessive gene linked to gender

AIII AII

cord blood, nasal swabs and stools. After the animal’s death, the

and Asia), which would probably indicate a worldwide distribution of infection by this virus.

RT-PCR and serology techniques for the detection of APPV genome

No

<4 months

No

Both

Moderate/high

with the techniques used in the programmes of diagnostic and epidemiological surveillance for the detection of CSFV and antibodies against this virus.

Duration of the clinical outbreak

Occurrence in subsequent litters of the same sow

Breed predisposition

Affected sex

Histopathology detects evidence (sometimes very subtle) of hypoMortality among affected piglets

>40 %

High Percentage of affected litters

Cause

Percentage of affected piglets within the litter

CSFV

AI

and antibodies against APPV are specific, so they do not interfere

CT (type)

Table 1. Causes and clinical and epidemiological characteristics of the different types of CT.

Intoxication; organophosphate poisoning

samples that can be taken in vivo, such as whole blood, umbilical

myelination of the CNS, but it does not discriminate between the variants of CT type A. With CT type AI (caused by CSFV), cerebellar hypoplasia is observed, which is not the case in the other CT variants.

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The publishing strength of Grupo AsĂ­s Editorial Servet, a division of Grupo AsĂ­s, has become one of the reference publishing companies in the veterinary sector worldwide. More than 15 years of experience in the publishing of contents about veterinary medicine guarantees the quality of its work. With a wide national and international distribution, the books in its catalogue are present in many different countries and have been translated into nine languages to date: English, French, Portuguese, German, Italian, Turkish, Japanese, Russian and Chinese.

Its identifying characteristic is a large multidisciplinary team formed by doctors and graduates in Veterinary Medicine and Fine Arts, and specialised designers with a great knowledge of the sector in which they work. Every book is subject to thorough technical and linguistic reviews and analyses, which allow the creation of works with a unique design and excellent contents.

Servet works with the most renowned national and international authors to include the topics most demanded by veterinary surgeons in its catalogue. In addition to its own works, Servet also prepares books for companies and the main multinational companies in the sector are among its clients.

Communication services Online visualisation of the sample chapter.

Presentation brochure in PDF format, compatible with mobile devices.

Servet (División de Grupo Asís Biomedia S.L.) Centro Empresarial El Trovador, planta 8, oficina I Plaza Antonio Beltrán Martínez, 1 • 50002 Zaragoza (España) Tel.: +34 976 461 480 • Fax: +34 976 423 000 • www.grupoasis.com