Almost 500 sickened: German pigs and Salmonella

In 2013, raw pork was the suspected vehicle of a large outbreak (n = 203 cases) of Salmonella Muenchen in the German federal state of Saxony. In 2014, we investigated an outbreak (n = 247 cases) caused by the same serovar affecting Saxony and three further federal states in the eastern part of Germany.

Evidence from epidemiological, microbiological and trace-back investigations strongly implicated different raw pork products as outbreak vehicles. Trace-back analysis of S. Muenchen-contaminated raw pork sausages narrowed the possible source down to 54 pig farms, and S. Muenchen was detected in three of them, which traded animals with each other. One of these farms had already been the suspected source of the 2013 outbreak. S. Muenchen isolates from stool of patients in 2013 and 2014 as well as from food and environmental surface swabs of the three pig farms shared indistinguishable pulsed-field gel electrophoresis patterns.

Our results indicate a common source of both outbreaks in the primary production of pigs. Current European regulations do not make provisions for Salmonella control measures on pig farms that have been involved in human disease outbreaks. In order to prevent future outbreaks, legislators should consider tightening regulations for Salmonella control in causative primary production settings.

Two consecutive large outbreaks of salmonella muenchen linked to pig farming in Germany, 2013 to 2014: Is something missing in our regulatory framework?

Eurosurveillance, vol. 22, no. 18, 4 May 2017, A Schielke, W Rabsch, R Prager, S Simon, A Fruth, R Helling, M Schnabel, Siffczyk, S Wieczorek, S Schroeder, B Ahrens, H Oppermann, S Pfeiffer, SS Merbecks, B Rosner, C Frank, AA Weiser, P Luber, A Gilsdorf, K Stark, D Werber

First we take Manhattan, then Berlin: Zoonoses in the food chain

I may have spoken at this in 1998.

quote-first-we-take-manhattan-then-we-take-berlin-leonard-cohen-87-88-65Or something else.

My parents warned me Germans would not get my sense of humor, and I hobbled around Berlin with my first affliction of what I later understood to be familial-associated gout.

The beer probably didn’t help.

Regardless, the occurrence of zoonotic pathogens and toxigenic bacteria in the food chain and the associated risk for humans were the focus of the4th Symposium for Zoonoses and Food Safety” at the Federal Institute for Risk Assessment (BfR) in Berlin.

Around 250 participants were discussing strategies to combat zoonotic pathogens in livestock, their occurrence in foods of animal origin and the role of toxigenic bacteria for food safety.

“The sharp decline of salmonellosis in humans in recent years can be seen as a success of the measures taken to combat this pathogen in poultry flocks,” says BfR President Professor Dr. Dr. Andreas Hensel. “Accordingly, there is now more focus on other sources of human infection”. This includes the occurrence of Salmonella in pig farming and in reptiles kept as pets.

For this reason, the symposium also focused on how to reduce the spread of salmonella in pig herds and pork meat. To do so, the food chain was examined from feedstuffs all the way through to food retail. New goals and initiatives of the federal states were presented too. The possible role of household pets as a source of infection for humans was also thematised using the example of reptiles.

The risk posed to humans by other zoonotic pathogens was also looked at. New laboratory methods play an important role in estimating these risks and assessing possible infection chains. This was illustrated by describing the investigation of a listeriosis outbreak. Another current example is the appraisal of the gut bacteria Clostridium difficile as a zoonotic pathogen.

one-healthA second main focus of the symposium was toxigenic bacteria. These are bacteria whose metabolites can trigger illnesses known as food intoxications (poisonings) that can sometimes be severe. It is not the bacterium but rather the toxin produced by it that is the cause of the health impairment.

The number of cases of foodborne diseases through toxigenic bacteria reported on EU level is increasing continuously. With approx. 16%, overall food intoxications took third place in reported cases of foodborne disease outbreaks after viruses and salmonella in 2014.

The main focus of the symposium was on the significance, occurrence and detection of toxigenic Staphylococci, Bacilli and Clostridia. The results of outbreak investigations in Germany were presented among other things, along with suitable examination methods for detecting toxigenic bacteria in prepared foods. The experts also picked up on the question of whether more efforts have to be made to better estimate and minimise the risk posed by toxigenic bacteria in the future.


The real-life diseases that spread the vampire myth

Whenever I talk about Kansas, I think of a couple of times Amy and I went off the regular roads, and saw all kinds of pioneer homesteads, long abandoned but probably built about the 1820s.

finger-of-godGiven the weather of Kansas, I would speculate, it’s no wonder so many crazy religions came from this place, because the finger of god – tornadoes – would descend without warning, super heat, super cold, and it wasn’t like anyone could go to Wal-Mart and restock.

It was probably terrifying.

I also recall how an astounding professor who’s class I got to TA for a couple of years – genetics for arts students – would begin every semester by citing Christian scripture and then describe the genetic ailment (he also said the Christian bible was a fairytale, because a woman – XX – could only have a female offspring and still be a virgin).

Vampires are the same way.

Stephen Dowling of the BBC writes diseases were frightening things before the age of medical science. Plagues and epidemics could appear without warning and cause death and misery (I’m thinking Jesus time and Kansas, 1820).

It wasn’t just plagues. Other diseases – perhaps passed on by animals or from genes lying dormant in their own bodies – could cause ailments that defied explanation.

People turned instead to the supernatural. Some of these diseases helped spawn one of the most enduring and widespread monster myths in civilisation – the vampire.

The vampire – an undead figure who rises each night from his unquiet grave to feast on the blood of the living – has appeared since the time of the Ancient Greeks. While some of the sage old philosophers we still admire today might have lived into their 70s, life expectancy in Ancient Greece was thought to be around 28; centuries before sanitation, refrigeration and antibiotics, diseases were more prevalent and were far more likely to take people to an early grave.

But without a microscope to study these tiny assailants, communities in older times saw the hand of the supernatural in many diseases.

Author Roger Luckhurst, who edited Oxford World’s Classic’s reprint of Bram Stoker’s Dracula, has researched the conditions which spread the belief in vampires, showing that the myth began to gain popularity in the early 18th Century. “The first mention of the word vampire in the English language is in the 1730s, in newspapers which carry reports from the edge of Europe, of bodies being dug up and looking bloated, and having fresh blood around their mouths. They report that these stories have come from peasants, but they make them sound very plausible.”

When calamity struck these rural areas – plague, cattle dying – many would point the finger at an undead spirit preying on the living. Often the first act would be to dig up the last person who had died in the village. And that leads us to another problem – medical science was in such infancy, that even telling if a person had died wasn’t exactly foolproof. Diseases such as catalepsy, which put people into a catatonic state so deep that their pulse was hard to detect, meant some were buried alive. If they awoke, some were driven so mad with fear and hunger that they would bite themselves – an explanation, perhaps, for some of the corpses found with fresh blood.

Most people in these communities kept animals; the villages themselves were usually close to forests and woodlands home to many other animals. Before vaccination was discovered, rabies, now virtually unknown in the European wild, was common. Once symptoms – which include aversion to light and water, aggression, biting and delirium – developed, death was inevitable. There is no cure.

“Rabies is obviously where we get the link to the werewolf, too,” says Luckhurst. “People were turned feral by this contact with animals. There is a degree of folk wisdom in the werewolf myth, a warning for people not to connect yourself too much to the natural world. You had to remember your humanity.”

There are many cultures around the world – in different continents and at different times – that share the myth of the bloodsucking undead. There are manananggal in the Philippines, and the peuchen of Chile; the Baobhan Sith of Scotland and the Yara-ma-yha-who of indigenous Australian tribes.

Essentially, the vampire myth comes from more than just disease, says Luckhurst. The vampire always seems to come from somewhere outside of the comforts of our own homes – be that a rural Transylvanian cottage, an English stately home or Ancient Athens.

“It always comes from somewhere else; in Ancient Greece the barbarians from beyond the Greek world were cannibals and bloodsuckers, and able to do all sorts of black magic that they were weren’t. In other places, it was the pagan tribes.” Even in South America, he says, the vampiric creatures the Incas believed in were from the wilds beyond their cities.

The vampire seems to be a vehicle not just for the diseases that we were not able to comprehend, but for all those strange, unmapped places and the people that live in them too.

Would I lie to you: Reducing risk of disease in dogs (and humans)

Approximately 35% of households in the United States and Canada own 1 or more dogs, totaling an estimated 75 million dogs in the United States and Canada. Despite continuous development of health promotion and disease prevention products and strategies, infectious disease remains an important contributor to disease and death for dogs. Hundreds of pathogens infectious to dogs have been identified, with more emerging over time.3 Some of these pathogens can also cause disease in people, leading to published recommendations to reduce the risks of human disease associated with animal settings.

sadie-dog-powellMany opportunities for transmission of infectious disease are amplified when dogs are brought together in a shared environment. Settings that involve the temporary congregation of numerous dogs for competition, play, or boarding (often from various geographic locations) are of particular infectious disease concern. Such canine group settings are popular; some of these activities may involve thousands of dogs attending events over several days. Infectious agents introduced into these group settings may lead to disease outbreaks, with the potential for further spread into the communities where the dogs reside, putting many dogs (and potentially humans) at risk.

The process of preventing or reducing the transmission of infectious diseases is complex. Disease agents vary in environmental stability, transmission modes, infectivity (ability to spread between hosts), pathogenicity (ability to cause disease), and virulence (ability to cause severe disease). Additionally, a combination of individual-, population-, and environment-level factors influences the development of infectious diseases in dogs. Individual-level factors include age, immune and health status, acquired immunity (previous infection or vaccination), diet, preventive care (eg, ecto- and endoparasite control), and hand hygiene by the people that handle them. Population- or event-level factors include herd immunity, dog density, event cleaning and disinfection practices, and degree of direct and indirect dog-to-dog contact. Environment-level factors include exposure to infectious agents through pathogen-infected vectors (influenced by geography, time of year, and degree of contact with vector-dense locations) or wildlife or their contaminated environment (eg, urine- or feces-contaminated water).

Some factors have individual- and event-level components requiring an integrated approach to risk management. For instance, to reduce indirect pathogen spread, individual efforts, such as the practice of hand hygiene between handling of dogs and use of effective disinfectants, must complement event-level procedures, such as policies and availability of disinfectant and hand hygiene products.

Given the complexity and importance of integrating individual- and event-level efforts, effective disease prevention in canine group settings would be facilitated by evidence-based guidelines that could be widely disseminated and flexibly applied to create disease prevention, risk mitigation, and control programs. In human group settings, disease prevention programs involving standards, recommendations, and regulations are commonly used; similar programs are also being applied in equine group settings. On the other hand, limited standards, guidelines, recommendations, or regulations currently exist regarding infectious disease prevention for canine group settings. For instance, the American Kennel Club has limited rules for addressing infectious disease opportunities during its dog events, and although policies have been developed for many dog parks and privately owned boarding facilities, no standard set of recommendations exists to guide such policies.

Animal shelters house concentrated populations of dogs and have developed resources to guide disease prevention and control programs in their facilities; however, such settings involve a largely unowned population, necessitating somewhat different strategies. The objectives of the literature review reported here were to identify the specific risks of infectious disease transmission among owned dogs in transient group settings in the United States and Canada and use this information to develop prevention and control recommendations.

Risk reduction and management strategies to prevent transmission of infectious disease among dogs at dog shows, sporting events, and other canine group settings

Journal of the American Veterinary Medical Association

September 15, 2016, Vol. 249, No.6

Stull et al

Hep E? From pigs? In Corsica?

To the Editor: In Western countries, human infection with hepatitis E virus (HEV) is mostly autochthonous and zoonotic through ingestion of contaminated food or direct contact with infected animals and very occasionally is imported from regions to which it is endemic to humans (tropical and subtropical areas) (1). Domestic pigs and wild boars are important zoonotic reservoirs of HEV worldwide (2).

pigwapplesmIn continental France, grouped cases of hepatitis E have been described after ingestion of Corsican specialties made with raw pig liver known as ficatelli, traditionally eaten grilled or raw after curing (3,4). A survey of French food products detected HEV RNA in 30% of ficatelli samples (5). A recent nationwide study of blood donors in France showed a high (>60%) HEV seroprevalence in Corsica, suggesting local hyperendemicity (6). Estimated prevalences of HEV RNA from wild boars and domestic pigs in Corsica were 2.3% and 8.3%, respectively (F. Jori, unpub. data). We aimed to evaluate, at a molecular level, the role of local wild boars and domestic pigs from Corsica in human infections or food contaminations.

We retrieved partial sequences of HEV open reading frame 2 capsid (7) from samples from 8 wild boars hunted during 2009–2013 and from 2 domestic pigs collected at a slaughterhouse in 2013 (F. Jori, unpub. data) and compared them with sequences available in GenBank. This genomic region is used frequently in phylogeny and reflects the diversity of HEV (8). After alignment with reference sequences for subtyping (9) and their closest sequences, we constructed a phylogenetic tree (Figure). All 10 sequences belonged to HEV genotype 3 and were distributed into 3 distinct clusters.

Cluster 1, subtype 3c, comprised 4 wild boar sequences (FR-HEVWB-1-91, FR-HEVWB-3-07, FR-HEVWB-7-114, FR-HEVWB-8-115) that had 96%–97% nt identity. These sequences were identified during 3 successive hunting seasons (2009, 2010, and 2013) in the same hunting area, suggesting that HEV sequences can be stable, with limited genetic variability, during at least 4 years in a local population of wild boars. These sequences were close to HEV wild boar sequences from Belgium (GenBank accession no. KP296177) and Germany (GenBank accession no. FJ705359; 3c reference sequence). A possible introduction of wild boars from northeast continental France into Corsica during the 1990s could explain such similarity (C. Pietri, pers. comm.). Two human cases reported in southeastern France (GenBank accession nos. GQ426997, KJ742841) in 2008 and 2009 also aggregated within this cluster (94%–95% nt identity), indicating possible zoonotic transmissions from wild boars to humans.

Cluster 2 comprised 2 wild boar sequences (FR-HEVWB-2-101 and FR-HEVWB-6-75) with 99.3% nt similarity, collected in 2009 and 2012 from the same geographic area (Haute Corse, <10 km apart). This cluster is distant from the subtypes assigned by Smith et al. (9) and shows <86.5% nt identity with reference sequences (Figure), indicating a possible local and stable evolution in space and time.

Cluster 3, subtype 3f, comprised sequences isolated from wild boars and domestic pigs from Corsica, humans from continental France, and 1 food sample from Corsica. The 2 domestic pig sequences (FR-SHEV-2B-1-182, FR-SHEV-2B-2-190) were 100% identical and shared 97.5% nt identity with a wild boar sequence (FR-HEVWB-4-104), suggesting transmission between domestic and wild pigs. These 2 swine sequences shared 96% nt identity with a sequence amplified in 2011 from a ficatellu sample (FR-HEVFIG-3; GenBank accession no. KJ558438) (5) from the same geographic area of Corsica (Haute Corse) and 96% nt identity with an isolate from a patient with acute hepatitis E recorded in France in 2009 (GenBank accession no. JF730424). In addition, the wild boar sequence in this cluster (FR-HEVWB-4-104) shared 96.4% nt identity with the same ficatellu sample and 97.1% nt identity with the same patient in France. This finding suggests that some locally produced ficatelli could be contaminated with HEV from local domestic pigs or wild boars. The human infection also suggests that zoonotic transmission might have occurred through contact with local pig or wild boar reservoirs or through ingestion of contaminated food products. No additional information is available about this human case that might attribute the contamination to 1 of the sources.

Also in cluster 3, another Corsican wild boar sequence (FR-HEVWB-5-117), isolated in 2011, shared 96.2% and 95.7% nt identity with 2 human sequences identified from continental France in 2013 (GenBank accession no. KR027083) and 2009 (GenBank accession no. JF730424 FR-HuHEV-09AL38). This finding again suggests a zoonotic origin for these human cases. Cluster 3 illustrates well a possible path of transmission between wildlife, domestic pigs, food, and human infection and the potential for dissemination of HEV outside Corsica.

pig.sex_Our results provide evidence suggesting a dynamic exchange of HEV between domestic and wild swine reservoirs and possibly resulting in transmission from those reservoirs to humans through ingestion of infected food products. These animal reservoirs are common and abundant ( and represent a sustainable source of HEV exposure in Corsica.

Nicole Pavio , Morgane Laval, Oscar Maestrini, François Casabianca, François Charrier, and Ferran Jori

Author affiliations: ANSES (French Agency for Food, Environmental and Occupational Health and Safety); Maisons-Alfort, France (N. Pavio); INRA (National Institute for Agricultural Research); Maisons-Alfort (N. Pavio); University Paris 12, National Veterinary School, Maisons-Alfort (N. Pavio); INRA, Corte, France (M. Laval, O. Maestrini, F. Casabianca, F. Charrier); CIRAD (Agricultural Research for Development); Montpellier, France (F. Jori); Botswana University of Agriculture and Natural Resources, Gaborone, Botswana (F. Jori)


We are grateful to Gaël Stéphant for technical assistance in swine sample analysis. We thank Christian Pietri for sharing his knowledge on the origin of wild boar population in Corsica.

Part of the study including wild boar and domestic pig sample analysis was supported by the European Union Seventh Framework Program (FP7/2007-2013) under grant agreement no. 278433-PREDEMICS and grant agreement no. 311931 (ASFORCE).


1.Pavio N, Meng XJ, Renou C. Zoonotic hepatitis E: animal reservoirs and emerging risks. Vet Res. 2010;41:46. DOIPubMed

2.Thiry D, Mauroy A, Pavio N, Purdy MA, Rose N, Thiry E, Hepatitis E virus and related viruses in animals. Transbound Emerg Dis. 2015;n/a; Epub ahead of print. DOIPubMed

3.Colson P, Borentain P, Queyriaux B, Kaba M, Moal V, Gallian P, Pig liver sausage as a source of hepatitis E virus transmission to humans. J Infect Dis. 2010;202:825–34. DOIPubMed

4.Renou C, Roque-Afonso AM, Pavio N. Foodborne transmission of hepatitis E virus from raw pork liver sausage, France.[Erratum in: Emerg Infect Dis. 2015;21:384. ]. Emerg Infect Dis. 2014;20:1945–7.DOIPubMed

5.Pavio N, Merbah T, Thébault A. Frequent hepatitis E virus contamination in food containing raw pork liver, France.Emerg Infect Dis. 2014;20:1925–7. DOIPubMed

6.Mansuy JM, Gallian P, Dimeglio C, Saune K, Arnaud C, Pelletier B, A nationwide survey of hepatitis E viral infection in French blood donors. Hepatology. 2016;63:1145–54. DOIPubMed

7.Rose N, Lunazzi A, Dorenlor V, Merbah T, Eono F, Eloit M, High prevalence of hepatitis E virus in French domestic pigs.Comp Immunol Microbiol Infect Dis. 2011;34:419–27. DOIPubMed

8.Lu L, Li C, Hagedorn CH. Phylogenetic analysis of global hepatitis E virus sequences: genetic diversity, subtypes and zoonosis. Rev Med Virol. 2006;16:5–36. DOIPubMed

9.Smith DB, Simmonds P, Izopet J, Oliveira-Filho EF, Ulrich RG, Johne R, Proposed reference sequences for hepatitis E virus subtypes. J Gen Virol. 2016;97:537–42. DOIPubMed

Possible foodborne transmission of Hepatitis E virus from domestic pigs and wild boars from Corsica

Emerging Infectious Diseases; Volume 22, Number 12—December 2016; DOI: 10.3201/eid2212.160612

Pavio N, Laval M, Maestrini O, Casabianca F, Charrier F, Jori F.

Animals as sources of human pathogens in Ecuador

Animals are important reservoirs of zoonotic enteropathogens, and transmission to humans occurs more frequently in low- and middle-income countries (LMICs), where small-scale livestock production is common.

Zoonoses_Image_0-270x252In this study, we investigated the presence of zoonotic enteropathogens in stool samples from 64 asymptomatic children and 203 domestic animals of 62 households in a semirural community in Ecuador between June and August 2014.

Multilocus sequence typing (MLST) was used to assess zoonotic transmission of Campylobacter jejuni and atypical enteropathogenic Escherichia coli (aEPEC), which were the most prevalent bacterial pathogens in children and domestic animals (30.7% and 10.5%, respectively). Four sequence types (STs) of C. jejuni and four STs of aEPEC were identical between children and domestic animals. The apparent sources of human infection were chickens, dogs, guinea pigs, and rabbits for C. jejuni and pigs, dogs, and chickens for aEPEC.

Other pathogens detected in children and domestic animals were Giardia lamblia (13.1%), Cryptosporidium parvum (1.1%), and Shiga toxin-producing E. coli (STEC) (2.6%). Salmonella enterica was detected in 5 dogs and Yersinia enterocolitica was identified in 1 pig. Even though we identified 7 enteric pathogens in children, we encountered evidence of active transmission between domestic animals and humans only for C. jejuni and aEPEC. We also found evidence that C. jejuni strains from chickens were more likely to be transmitted to humans than those coming from other domestic animals. Our findings demonstrate the complex nature of enteropathogen transmission between domestic animals and humans and stress the need for further studies.


We found evidence that Campylobacter jejuni, Giardia, and aEPEC organisms were the most common zoonotic enteropathogens in children and domestic animals in a region close to Quito, the capital of Ecuador. Genetic analysis of the isolates suggests transmission of some genotypes of C. jejuni and aEPEC from domestic animals to humans in this region. We also found that the genotypes associated with C. jejuni from chickens were present more often in children than were those from other domestic animals. The potential environmental factors associated with transmission of these pathogens to humans then are discussed.

Detection of zoonotic enteropathogens in children and domestic animals in a semirural community in Ecuador

Karla Vasco a, Jay P. Graham b and Gabriel Trueba a

A Microbiology Institute, Colegio de Ciencias Biologicas y Ambientales, Universidad San Francisco de Quito, Quito, Ecuador

B Milken Institute School of Public Health, George Washington University, Washington, DC, USA

Applied and Environmental Microbiology, Volume 82, Number 14, Pages 4218–4224, doi:10.1128/AEM.00795-16

Pretty pictures of zoonotic disease risk

The majority of infectious diseases currently emerging as human epidemics originated in mammals. Yet little is known about the global patterns of mammal-to-human pathogen transmission.

zoonoses.mapResearchers at the Cary Institute of Ecosystem Studies and the University of Georgia have assembled summative world maps of what’s on record about mammal-to-human diseases. The work, which aims to question whether it is possible to predict the emergence of new zoonotic diseases, appears June 14 as part of a Review in Trends in Parasitology.

The maps include data on all 27 orders of terrestrial mammals, including rabid bats, camels carrying Middle East respiratory syndrome, the hoofed relatives of livestock that pass on foodborne diseases, and many different kinds (more than 2,000 species) of rodents. Outbreaks of diseases caused by pathogens that originate in non-human hosts (called zoonoses) are believed to be inherently unpredictable, but the maps reveal understudied patterns.

Map data were partially generated from information in the Global Infectious Disease and Epidemiology Network (GIDEON) database as well as mammal distribution maps published by the International Union for the Conservation of Nature.

“Understanding where animals are distributed and why may not seem applicable to our day-to-day lives,” says first author Barbara Han, a disease ecologist at the Cary Institute of Ecosystem Studies in New York. “But the big breakthroughs that we need as a society (e.g., forecasting where the next zoonotic disease may emerge) rely on exactly this kind of basic scientific knowledge.”

Or as Worms and Germs Blogerer Scott Weese says, “The paper has a lot of comprehensive discussion of risks associated with various types of mammals (e.g. rodents vs bats vs ungulates) and various types of pathogens.

“However, since we tend to like things distilled down into pretty pictures, their maps are getting the most attention. Their assessment of the number of zoonoses in different regions might surprise some.”

An emerging pathogen: Helicobcter pullorum in chicken

Meat and meat products are important sources of human intestinal infections. We report the isolation of Helicobcter pullorum strains from chicken meat.

icarly.chicken.handsBacteria were isolated from 4 of the 17 analyzed fresh chicken meat samples, using a membrane filter method. MIC determination revealed that the four strains showed acquired resistance to ciprofloxacin; one was also resistant to erythromycin, and another one was resistant to tetracycline. Whole-genome sequencing of the four strains and comparative genomics revealed important genetic traits within the H. pullorum species, such as 18 highly polymorphic genes (including a putative new cytotoxin gene), plasmids, prophages, and a complete type VI secretion system (T6SS). The T6SS was found in three out of the four isolates, suggesting that it may play a role in H. pullorum pathogenicity and diversity.

This study suggests that the emerging pathogen H. pullorum can be transmitted to humans by chicken meat consumption/contact and constitutes an important contribution toward a better knowledge of the genetic diversity within the H. pullorum species. In addition, some genetic traits found in the four strains provide relevant clues to how this species may promote adaptation and virulence.

Helicobacter pullorum isolated from fresh chicken meat: Antibiotic resistance and genomic traits of an emerging foodborne pathogen

Applied and Environmental Microbiology, Volume 81, Number 23, December 2015

V Borges, A Santos, C Correia, M Saraiva, A Menard, L Viera, D Sampaio, M Pinheiro, J Gomes, M Oleastro


Damn you cats: Squirrels ‘dropping dead from trees’ from Toxo outbreak

Toxoplasma gondii, a zoonotic protozoan parasite for which felids are the only definitive hosts, can infect humans and other warm-blooded animals.

cats.sink.jun.13Transmission usually occurs orally from oocysts shed by felids in water and on food, through tissue cysts in undercooked meat, or transplacentally. In particular, young cats shed oocysts that can sporulate and become infectious within a day, depending on temperature and humidity. Sporulated oocysts can survive in moist soil for months to years (1).

In September 2014, the number of dead squirrels reported to the Dutch Wildlife Health Centre and the Dutch Mammal Society increased suddenly. The red squirrel (Sciurus vulgaris) is the only species of squirrel endemic to the Netherlands. Members of the public claimed that squirrels were “dropping dead from trees.” Subsequently, the public was encouraged to report and submit dead squirrels. A total of 187 animals were reported through October 2014, of which 37 were submitted for necropsy. Necropsy included macroscopic examination; cytologic analysis of liver, spleen, lungs, and intestinal contents stained with hemacolor (Merck, Darmstadt, Germany); and histologic examination of samples of various organs fixed in formalin, embedded in paraffin, cut into 4-μm sections, and stained with hematoxylin and eosin.

For 8 adult animals, body condition (based on degree of fat storage and muscle development) was good; 12 juveniles were in poor condition. Typically, the trachea contained foam, and lungs were hyperemic and edematous. The liver was enlarged and pale, and the spleen was enlarged. In 13 animals, numerous small crescent-shaped organisms, with eccentrically placed nuclei consistent with tachyzoites of T. gondii, were identified by cytology in lung, liver, and spleen (2). Main histopathologic findings were pulmonary interstitial lymphoplasmocytic and neutrophilic infiltrates with edema and numerous intra-alveolar macrophages (17/20) and multifocal lymphoplasmocytic infiltrates with necrosis in the liver (13/20). Extensive splenic necrosis was occasionally observed (4/20). Intestines contained mild plasmacytic infiltrates. Numerous tachyzoites consistent with T. gondii were present in alveolar macrophages and epithelial cells, splenic macrophages, and hepatocytes. Duplicate slides were stained immunohistochemically by using polyclonal antibodies against T. gondii following a standard ABC protocol (3). Organisms stained for T. gondii in liver, spleen, lungs, and intestine. Toxoplasma was not detected in any brain. DNA was isolated (DNeasy Blood and Tissue Kit; QIAGEN, Hilden, Germany) from tissues of 14 squirrels and tested by quantitative PCR (1); T. gondii DNA was detected in 13. We successfully sequenced the T. gondii GRA6 gene for 11 squirrels and identified sequences to clonal type II T. gondii previously identified in sheep from the Netherlands (GenBank accession no. GU325790) (4). Incidental findings in the animals tested were encephalitis (2/20), coccidiosis (5/20), trauma (6/20), myocarditis (4/20), nephritis (1/20), lymphadenitis (1/20), and intestinal (3/20) and external (5/20) parasites.

The remaining 17 animals showed >1 of the following pathologic conditions: hemorrhages consistent with trauma (12/17), mild to severe intestinal coccidiosis (12/17), pneumonia (3/17), splenitis (1/17), Taenia martis cysticerci (1/17), and external parasites (8/17). Immunohistochemistry results for all 17 were negative for T. gondii.

grey.squirrel.eatOn the basis of necropsy and molecular findings, we conclude that 20 of 37 examined squirrels died of disseminated T. gondii type II infection. These animals included adults and juveniles and were not restricted to specific geographic areas. The remaining animals died of trauma (12/17) or other causes (5/17).

Red squirrels are susceptible to T. gondii, and infection can lead to death. However, in our sample, the proportion of squirrels that died of toxoplasmosis (>50%) was higher than in other studies (≈16%) (5,6,7). The apparent increase in squirrel deaths and unexpectedly high proportion of fatal T. gondii infections suggests a toxoplasmosis outbreak among red squirrels. Possible explanations for this surge in cases include increased exposure to the parasite, increased susceptibility to infection, or increased virulence of the pathogen. Clonal T. gondii type II, the strain most frequently involved in human cases and endemic to Europe and North America, was identified. An increased virulence of the pathogen could not be proven (8). On the basis of lymphoid hyperplasia in the spleen and lymph nodes, affected squirrels had no signs of immunosuppression. Thus, the most likely explanation is increased exposure to the parasite.

Sources of infection for red squirrels are not known; however, oocysts shed in cat feces may contaminate the nuts, fungi, shoots, and berries that constitute the diet of the squirrel. Stray, unspayed cats are common in the Dutch countryside. More than 3 million domestic cats (Felis domesticus) exist in the Netherlands, including several tens of thousands of free-roaming cats that reproduce (9). Determining the exact source of infection is important because humans also harvest wild fruits, nuts, and fungi from these areas. This outbreak highlights that contamination of the environment with T. gondii oocysts is of concern not only from a public health viewpoint but from a biodiversity perspective as well (1,10).

Marja Kik Comments to Author , Jooske IJzer, Marieke Opsteegh, Margriet Montizaan, Vilmar Dijkstra, Jolianne Rijks, Andrea Gröne, and Jooske IJzer

Author affiliations: Utrecht University, Utrecht, the Netherlands (M. Kik, J. IJzer, M. Montizaan, J. Rijks, A. Gröne); Dutch National Institute for Public Health and the Environment, Bilthoven, the Netherlands (M. Opsteegh); Dutch Mammal Society, Nijmegen, the Netherlands (V. Dijkstra)


Toxoplasma gondii in Wild Red Squirrels, the Netherlands, 2014

Emerging Infections Diseases, Volume 21, Number 12, December 2015

Why inspectors fret about rats: Rodents as hosts of infectious diseases

Rodents are recognized as hosts of more than 60 zoonotic diseases that represent a serious threat to human health (Meerburg et al. 2009, Luis et al. 2013). This special issue emerges from a workshop organized in Bangkok at the Faculty of Veterinary Medicine of Kasetsart University and supported by the French ANR project CERoPath (Community Ecology of Rodents and their Pathogens in a Southeast Asian changing environment), which aimed at better understanding the relationships between rodent-borne diseases, rodents and their habitats using intensive field works, serology, and molecular screenings.

sq-willard-crispin-glover-rat-nlThe main objective of this workshop was to join ecologists, biologists, and epidemiologists to give an overview on the importance of rodents as hosts and reservoirs of parasitic and infectious diseases. Most of presentations given in the workshop focused in Southeast Asia, a hotspot of both infectious emerging diseases (Coker et al. 2011) and biodiversity at threat due to dramatic changes in land use (Morand et al. 2014).

A first challenge is related to the invasion or range expansion of rodents. The black rat (Rattus rattus), Norway rat (Rattus norvegicus), Asian house rat, (Rattus tanezumi) and Pacific rat (Rattus exulans) like the house mice (Mus musculus), have dramatically expanded their geographic range as a consequence of human activities (Aplin et al. 2011). All of these Rattus species originated in Asia, and can be found in sympatry due to their synanthropic behavior (McFarlane et al. 2012). These rodents have been implicated (Kosoy et al., this issue), and still are implicated (Kuo et al. 2011), in the emergence and spread of plague, murine typhus, scrub typhus, leptospirosis, hantavirus hemorrhagic fever, among others. A better comprehension of the range extension mechanisms and consequences in term of infectious diseases’ risks would require investigation of the genetics and immunology of these rodent species (Himsworth et al., this issue) as well on the ecological interactions among pathogens, vectors, and rodents. Gutiérrez et al. (this issue) in their review attempt to summarize and bridge some knowledge gaps in the transmission and distribution routes, and in the dynamics and composition of Bartonella-infection in rodents and their flea parasites.

A second challenge is that in order to better understand disease ecology and parasite transmission, it must be considered that not all hosts are equally involved in parasite transmission as some species (and individuals) can be responsible for a disproportionate number of transmission events (Paull et al. 2012). Some habitats or landscapes may also disproportionally enhance transmission or persistence of parasite and/or vector (Bordes et al. 2013). Indeed, by carrying and disseminating parasites across multiple habitats, generalist or synanthropic rodents could enhance both host-switching and spill-over to other rodent reservoirs and directly or indirectly to humans.

rat.restaurantSeveral articles in this special issue suggest high diversity of pathogens and parasites circulating among diversified communities of rodents across various habitats, such as Rickettsia spp. in Taiwan (Kuo et al., this issue), Bartonella spp. in Vietnam (Hoang et al., this issue) and in Thailand (Jiyipong et al., in this issue), leptospirosis in Vietnam (Hoang et al., this issue), zoonotic viruses in Vietnam (Cuong et al., this issue), and zoonotic helminths in Thailand (Chaisiri et al., this issue).

This special issue calls for a more thorough investigation of rodent-borne diseases taking into account the ecology of rodents in their habitats. Taken together, the studies presented in this special issue stress the need to identify the mechanisms affecting pathogen diversity and infection within and between rodent species and to explain why some rodent species seem to be more resilient to greater habitat disturbance. Future research should monitor a variety of rodent pathogens simultaneously, including directly-transmitted specific pathogens and vector-borne pathogens with varying degrees of specificity.

Vector-Borne and Zoonotic Diseases. January 2015, 15(1): 1-2.

Morand S., Jittapalapong S., and Kosoy Michael