Papers by D. Gavier-widén
The pathology, frequency and diagnostic implications of ‘no visible lesion’ (NVL) tuberculosis (T... more The pathology, frequency and diagnostic implications of ‘no visible lesion’ (NVL) tuberculosis (Tb), i.e. infection with Mycobacterium bovis in the absence of macroscopic lesions, are described in a wide taxonomic range of wildlife hosts. Information collected and evaluated on the definition and occurrence of NVL Tb, histopathological characteristics, post-mortem techniques to detect minimal lesions, and diagnostic difficulties revealed most Tb-infected individuals with NVL had minute tuberculous lesions, which were difficult to see by eye. Acidfast organisms (AFO) were sometimes detected in the lesions. Ideally, mycobacterial culture of pools of lymph nodes and/or oropharyngeal tonsils is necessary for the accurate diagnosis of Tb in the absence of macroscopic lesions. At a very minimum, the diagnostic methods applied for studying the prevalence of Tb in the population should be clearly described, to allow comparison between studies.
To investigate the current status of forensic veterinary pathology, a survey was composed directe... more To investigate the current status of forensic veterinary pathology, a survey was composed directed at pathology laboratories and institutes, mostly in Europe. The questions included number of and type of cases, resources available, level of special training of the investigating pathologists and the general view on the current status and future of the discipline. The surveys were sent to 134 laboratories and were returned by 72 respondents of which 93 per cent work on forensic pathology cases. The results indicate scarcity of training opportunities and special education, and insufficient veterinary-specific reference data and information on forensic analyses. More cooperation with human forensic pathology was desired by many respondents, as was more interaction across country borders.
Liver lesions were studied in 40 free-living adult European brown hares (Lepus europaeus) and var... more Liver lesions were studied in 40 free-living adult European brown hares (Lepus europaeus) and varying hares (Lepus timidus) of both sexes that had died in Sweden with the viral infection European brown hare syndrome (EBHS). The lesions were characterized by their histopathologic, immunohistochemical, and electron microscopic findings. Periportal to massive coagulation necrosis was a distinctive feature of EBHS. Lytic necrosis, inflammation, fatty degeneration, and cholangitis occurred variably. Accumulation of basophilic granules in the cytoplasm of hepatocytes was commonly observed; these lesions corresponded ultrastructurally to mitochondrial calcification. Viral antigen was revealed in the cytoplasm and nucleus of hepatocytes and in the cytoplasm of macrophages.
The occurrence of Anaplasma phagocytophilum was investigated in spleen and serum samples from Swe... more The occurrence of Anaplasma phagocytophilum was investigated in spleen and serum samples from Swedish moose (Alces alces) in southern Sweden (island and mainland). Samples were analysed for presence of A. phagocytophilum DNA by real-time PCR (n = 263), and for Anaplasma antibodies with ELISA serology (n = 234). All serum samples had antibodies against A. phagocytophilum. The mean DNA-based prevalence was 26•3%, and significant (P < 0•01) temporal, and spatial variation was found. Island moose had significantly (P < 0•001) higher prevalence of A. phagocytophilum DNA than moose from the mainland areas. Two samples were sequenced to determine genetic variation in the 16S rRNA and groESL genes. Genetic sequence similarity with the human granulocytic anaplasmosis agent, equine granulocytic ehrlichiosis agent, and different wildlife-associated A. phagocytophilum variants were observed in the 16S rRNA and groESL genes. Our study shows that moose are exposed to A. phagocytophilum in Sweden, and represent a potential wildlife reservoir of the pathogen.
Understanding and combatting African Swine Fever
African swine fever (ASF) is a haemorrhagic viral disease of domestic pigs and wild boar (both Su... more African swine fever (ASF) is a haemorrhagic viral disease of domestic pigs and wild boar (both Sus scrofa species) that seriously impacts pig production worldwide. Pathology plays a key role not only in identifying and characterising macroscopic and histopathological lesions, but also in studying pathogenesis, thus complementing other disciplines to provide a broad understanding of host-virus interactions, which contributes to the development of vaccines and therapies. The aim of the present chapter is to provide a compilation of the most characteristic macroscopic and histopathological lesions associated with the different clinical forms of ASF (peracute, acute, subacute and chronic). Another aim is to present the current state of knowledge regarding ASF pathogenesis, with special attention to target cells, virus distribution and virus load in multiple organ locations and its correlation with the appearance of clinical signs and lesions from early stages to terminal disease. For that purpose, the chapter includes a complete collection of original macroscopic and microscopic photographs, the latter including illustrations of haematoxylin and eosin-stained sections and immunohistochemistry to identify the ASF-virus (ASFV). The photographs were obtained from experimental infections with ASFV isolates of different virulence carried out over the last two decades in different research centres. The purpose is to provide a reference that may be useful for the early recognition of ASF by veterinary practitioners working in the field and researchers focused on characterising new ASFV isolates or testing new vaccines and treatments.
Understanding and combatting African Swine Fever
More than one hundred years ago African swine fever (ASF) was first diagnosed in Kenya. Since the... more More than one hundred years ago African swine fever (ASF) was first diagnosed in Kenya. Since then, diverse approaches have been applied to the study of the causative virus, the sole member of the family Asfarviridae, aimed at characterising its properties, genome organisation and replication, its antigenic and biological properties as well as to develop treatment and a vaccine. The disease evolved and has persisted in Africa in a sylvatic cycle involving wild suids and soft ticks for a long time, but was introduced, usually through contaminated waste food, into other regions on multiple occasions since 1957. The most recent introduction, into Georgia in 2007, resulted in the spread of the disease to the European Union in 2014 and to the establishment of an international and multidisciplinary network of scientists funded by the European Cooperation in Science and Technology (COST) two years later. The network included a broad variety of scientific fields, animal health and food safety authorities, hunting associations, wildlife managers and food and livestock industries with the goal of increasing preparedness and attempting to stop ASF spread. This book represents the summary of the collective and integrated work of almost 300 dedicated participants in tackling the complex challenge posed by ASF. Here we summarise the state-of-the-art knowledge on this lethal disease, with a focus on the European situation, and identify areas that still need to be explored.
Epidemiology and Infection
Tularaemia is a zoonotic disease, in Europe caused by Francisella tularensis subsp. holarctica. M... more Tularaemia is a zoonotic disease, in Europe caused by Francisella tularensis subsp. holarctica. Many lagomorphs and a variety of small rodents are wildlife species prone to develop clinical disease, while predators and scavengers are relatively resistant and may serve as sentinels. Blood samples from 656 Swedish wild predators and scavengers were serologically investigated using slide agglutination and microagglutination. In the slide agglutination test, 34 seropositive animals were detected, and they were found among all species investigated: brown bear (Ursus arctos), Eurasian lynx (Lynx lynx), raccoon dog (Nyctereutes procyonoides), red fox (Vulpes vulpes), wild boar (Sus scrofa), wolf (Canis lupus) and wolverine (Gulo gulo). Due to haemolysis the microagglutination test was more difficult to read at low titres, and only 12 animals were classified as seropositive. F. tularensis subsp. holarctica was detected by a polymerase chain reaction in lymphatic tissues of the head in one b...
Epidemiology and Infection
SUMMARYTularemia caused by the bacterium Francisella tularensis is a zoonotic disease. Tularemia ... more SUMMARYTularemia caused by the bacterium Francisella tularensis is a zoonotic disease. Tularemia is a common disease in the hare, and as a game species can be an important source of infection for humans. In this study, hares diagnosed with tularemia were examined with the aim to investigate whether the muscle (meat) had any pathological changes and/or contained F. tularensis. Real-time PCR and/or immunohistochemistry (IHC) detected the bacteria in muscle samples from 40 out of 43 investigated hares. IHC showed that bacteria were few and most commonly located in the peri- and endomysium. Histopathology showed occasional perimysial necroses and mild inflammation in association to the bacteria. Attempts to culture from 14 muscle samples were successful in two cases, both stored in the freezer <1 year. The result of this study shows that since F. tularensis is present in the muscle of infected hares, there is a risk for human infection when consuming undercooked hare meat. The risk i...
Transboundary and Emerging Diseases
Rabbit haemorrhagic disease virus (RHDV) is a lagovirus that can cause fatal hepatitis (rabbit ha... more Rabbit haemorrhagic disease virus (RHDV) is a lagovirus that can cause fatal hepatitis (rabbit haemorrhagic disease, RHD) with mortality of 80-90% in farmed and wild rabbits. Since 1986, RHDV has caused outbreaks in rabbits (Oryctolagus cuniculus) in Europe, but never in European brown hares (Lepus europaeus, EBH). In 2010, a new RHDV-related virus, called RHDV2, emerged in Europe, causing extended epidemics because it largely overcame the immunity to RHDV present in most rabbit populations. RHDV2 also was identified in Cape hare (Lepus capensis subsp. mediterraneus) and in Italian hare (Lepus corsicanus). Here, we describe two distinct incidents of RHDV2 infection in EBH that occurred in Italy (2012) and Spain (2014). The two RHDV2 strains caused macroscopic and microscopic lesions similar to European brown hare syndrome (EBHS) in hares, and they were genetically related to other RHDV2 strains in Europe. EBHs are common in Europe, often sharing habitat with rabbits. They likely have been exposed to high levels of RHDV2 during outbreaks in rabbits in recent years, yet only two incidents of RHDV2 in EBHs have been found in Italy and Spain, suggesting that EBHs are not a primary host. Instead, they may act as spillover hosts in situations when infection pressure is high and barriers between rabbits and hares are limited, resulting in occasional infections causing EBHS-like lesions. The serological survey of stocked hare sera taken from Italian and Spanish hare populations provided an understanding of naturally occurring RHDV2 infection in the field confirming its sporadic occurrence in EBH. Our findings increase the knowledge on distribution, host range and epidemiology of RHDV2.
Open-File Report
Cover images, clockwise, starting top left: Top left, USGS scientist measures the tarsus length o... more Cover images, clockwise, starting top left: Top left, USGS scientist measures the tarsus length of a double-crested cormorant for a study on Newcastle disease virus (USGS photo). Top right, USGS scientist taking samples from a cave for a study on white-nose syndrome in bats (USGS photo). Bottom right, USGS biological science technician testing samples for avian influenza virus by inoculating embryonating eggs (USGS photo). Bottom left, USGS scientist inspecting wing of a bald eagle that will be tested for lead poisoning (USGS photo). Background photo of snow geese (Photo by Bob Dusek).
Transboundary and Emerging Diseases
Journal of Comparative Pathology
Tularaemia is an emerging zoonotic infectious disease caused by the bacterium Francisella tularen... more Tularaemia is an emerging zoonotic infectious disease caused by the bacterium Francisella tularensis. In Sweden, hares are considered to be key species in the epidemiology of tularaemia. The aim of this study was to characterize the pathology of natural tularaemia infection in European brown hares (EBHs) (Lepus europaeus) and mountain hares (MHs) (Lepus timidus) in Sweden, in order to better understand the presentation of disease and the routes of infection, body dissemination and shedding of F. tularensis. During 2000-2013, 49 EBHs and 37 MHs were diagnosed with tularaemia. Enlargement of the spleen was seen in 80% of EBHs and 62% of MHs. Necrosis was often obvious in the bone marrow, liver, lung and spleen, but 30% of the hares had no lesions or minimal gross lesions. On microscopical examination of tissues from 27 EBHs and three MHs, necrosis was seen in the majority of samples of liver, spleen, bone marrow, lymph node and adrenal glands and was common in the lungs and brain meninges. Immunohistochemistry for Francisella spp. detected bacteria in association with necrosis and inflammation. In several cases, Francisella spp. were also found inside blood vessels, in the renal pelvis, in lactating mammary glands, in bronchioles and in the skin, associated with tick bites. Using quantitative polymerase chain reaction, two genotypes of F. tularensis subsp. holarctica were found; canSNP group B.6, all belonging to subgroup B.7, and canSNP group B.12. There were no differences in pathology between the genotypes. Our results indicate that the urinary tract and mammary glands are important routes for the shedding of F. tularensis. Hunters may not be aware of the risks of contracting tularaemia while handling hares, since infected hares do not always show noticeable gross lesions.
Animal health research reviews / Conference of Research Workers in Animal Diseases, 2001
Only limited data concerning the prevalence of intestinal spirochetes are available in game birds... more Only limited data concerning the prevalence of intestinal spirochetes are available in game birds. This paper describes the prevalence and biochemical reactions of spirochetes isolated from 25 common partridges, 7 pheasants and 16 mallards originating from nine Swedish game-bird farms. The birds, which had been submitted for post-mortem examination due to various problems, showed a variety of underlying diseases. Additionally, fecal droppings from 22 common partridges, 20 pheasants and 20 mallards obtained at one of the farms were included in the study. Intestinal spirochetes were isolated from 85.4% of the game birds and from 71% of the fecal droppings. Seven biochemical types were identified. Seventeen per cent of all isolates were classified as Brachyspira pilosicoli and 3% as B. intermedia. One isolate showed strong beta-hemolysis and a positive indole reaction that is consistent with B. hyodysenteriae. In addition, three previously unknown biochemical types were found. Unclassi...
Journal of zoo and wildlife medicine : official publication of the American Association of Zoo Veterinarians, 1999
Different subtypes of Listeria monocytogenes were isolated from various animal and environmental ... more Different subtypes of Listeria monocytogenes were isolated from various animal and environmental samples during an episode of increased mortality on a fallow deer (Dama dama) farm. During a 4-wk period, six fallow deer died, including four does, one fawn, and one adult buck. Prior to death, one of the does had exhibited central nervous system signs characteristic of listeriosis. Postmortem examination of the six deer showed no histologic changes typical of listeriosis, although inflammatory changes were present in several organs. Different subtypes of L. monocytogenes were isolated from brain samples from six deer, from fodder and soil from the deer feeding area, and from faces of some healthy animals on the farm. Listeria monocytogenes, which was frequently isolated in the environment of the farm, was considered the probable major cause of mortality in these fallow deer.
Acta veterinaria Scandinavica, 1993
Journal of Comparative Pathology, 2015
Preventive Veterinary Medicine, 2015
This study attempted to develop a list of priority pathogens. It is part of a European Union (EU)... more This study attempted to develop a list of priority pathogens. It is part of a European Union (EU) project dedicated to the surveillance of emerging or re-emerging pathogens of wildlife. Partners of the consortium established an initial list of 138 pathogens of concern, which was reduced to a smaller list of 65 pathogens likely to affect ruminants (i.e., the most costly animal group in the EU over the last 15 years). These 65 pathogens underwent a two-step, expert-based risk analysis: 92 experts graded them with respect to their global importance for animal welfare, species conservation, trade/economic impacts and public health. In step 2, the top 15 pathogens from step 1 were assessed by 69 experts considering seven weighted epidemiological criteria (pathogen variability, host specificity, potential for contagion, speed of spread, presence in Europe, difficulty of surveillance in wildlife and persistence in the environment) for which four options were possible. The responses concerned a wide geographic coverage. The resulting top-list pathogens were ranked as follows: 1. Salmonella enterica, 2. Coxiella burnetii, 3. foot-and-mouth disease virus, 4. Mycobacterium bovis, 5. bluetongue virus, and 6. European tick-borne encephalitis virus. The influence of the characteristics of the respondents, the importance of the levels of uncertainty/variability and the implication of the results are discussed. This work highlights the relevance of developing such lists for preparedness.
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Papers by D. Gavier-widén