Geographical Variation and Factors Associated to Seroprevalence of Canine Leishmaniosis in an Endemic Mediterranean Area

This article retrospectively analyses the spatial distribution and dog‐ and environmental‐level risk factors associated to Leishmania infantum seroprevalence among 807 asymptomatic dogs in the Municipality of Crevillente in Alicante in southeast Spain in 1999. They represented 60% of the dogs in this 103 km² area, with a human census of 27 034 people and 90% lived in Crevillente town. The estimated seroprevalence (95% confidence interval) in 714 dogs ≥1‐year old was 22% (19–25) however; it was 12% (8–15) in town dogs and 0–100% in other administrative zones. High–medium seroprevalence zone clustered along a northeast–southwest fringe and around the town. They comprised the highest and driest inhabited part of the municipality, where farmland was interspersed by residential detached houses, whilst null–low seroprevalence zones included larger farmland extensions and two small rural villages. Predominant vegetation and ground soil type were bush, non‐irrigated fruit trees and conglomerate crust and sandstone in medium–high seroprevalence zones and irrigated grassland and fruit trees and colluvial deposits in null–low seroprevalence zones. Random effects logistic regression indicated that the prevalence of infection with L. infantum was higher for dogs sharing residence with infected dogs, increased until 5–6 years old and with body weight and was associated to increasing conglomerate crust and low surface water in the dog’s zone of residence. The study confirms that L. infantum infection is endemic in this part of Spain and shows that prevalence can vary significantly within a small area depending on specific demographic and environmental factors conditioning the habitat of the local L. infantum vector, Phlebotomus perniciosus. It suggests similar low‐scale variability is present in other geographically variable endemic areas and should be investigated to design Leishmaniosis risk maps and cost‐effective, evidence‐based, targeted control interventions.     

Demographic and Environmental Risk Factors for Exposure to Lawsonia intracellularis in Horses in Israel

Equine proliferative enteropathy (EPE) is an enteric disease of foals that is caused by Lawsonia intracellularis. Clinical cases have been reported worldwide; however, data regarding the epidemiology of L. intracellularis in horses are scarce. Thus far, L. intracellularis has not been reported in the Middle East. The objectives of this study were to determine whether the causative agent of EPE exists in horses in Israel and in the Palestinian Authority and to define environmental and demographic risk factors for exposure. Fecal and serum samples were collected from horses from various regions of the country. The presence of L. intracellularis in horses in Israel was determined by real-time polymerase chain reaction (PCR), and seroprevalence was determined by enzyme-linked immunosorbent assay. One fecal sample of 136 tested (0.7%), was PCR positive. Sixty-seven sera samples (30.5%) of 220 horses in sentinel farms had anti-L. intracellularis antibodies. Low seroprevalence was found in foals both from Israel and from the Palestinian Authority (4.2% and 13.3%, respectively). In logistic regression models, geographical locations, management type, and age were found to be significant risk factors associated with seroprevlaence to L. intracellularis. No significant correlation was found between environmental variables and L. intracellularis seroprevalence after controlling for management type. These results support the existence of L. intracellularis in horses in both Israel and the Palestinian Authority. The reasons for the relatively low prevalence are currently not known and may be the result of different management, low exposure to free-living animals, and differences in environmental variables affecting the bacterial burden.     

Detection of Leishmania infantum DNA by real-time PCR in canine oral and conjunctival swabs and comparison with other diagnostic techniques

The use of non invasive sampling, such as collection of conjunctival swabs, as a diagnostic tool for the detection of Leishmania DNA is of interest. The purpose of this study was to evaluate the diagnostic utility of detecting Leishmania infection with the use of conjunctival swab samples in dogs living in a highly endemic area for leishmaniosis and to investigate, for the first time, the presence of Leishmania DNA in oral swabs in the same population. One hundred sixty-three dogs living outdoor and recruited in various provinces of Sicily were studied. Leishmania infantum indirect fluorescent antibody test (IFAT), delayed-type hypersensitivity reaction to leishmanin (DTH) and real-time PCR of blood (BL), lymph node (LN), conjunctival (CS) and oral swab (OS) samples were performed. The positive PCR percentages in LN, CS, OS and BL samples were: 24.5%, 22.1%, 8.7% and 5.5%, respectively. Serological and DTH positive percentages were 27.0% and 73.8%, respectively. Seropositive and LN-PCR positive dogs had a high likelihood to be positive by CS-PCR. The similar positive PCR percentages found in CS and LN samples suggest the use of CS-PCR as non-invasive alternative technique to LN-PCR for the detection of Leishmania infection in dogs. In addition, this study demonstrated, for the first time, the presence of Leishmania DNA in oral swabs in dogs.     

Epidemiological Aspects in the Leptospira spp. and Toxoplasma gondii Infection in Horses from Botucatu,São Paulo,Brazil

Leptospirosis and toxoplasmosis are zoonoses with high importance because of the economic and public health impact. This study was aimed to determine the seroprevalence of leptospirosis and toxoplamosis in 714 serum samples of horses from different farms from Botucatu, São Paulo, Brazil. The samples were researched for Toxoplasma gondii antibodies by indirect immunofluorescence antibody test (IFAT) and for Leptospira spp. antibodies by microscopic agglutination test. Of 714 serum samples, 128 (17.9%; 95% CI: 15.3%-20.9%) were positive for one or more serovars of Leptospira spp., with icterohaemorrhagiae, canicola, and castellonis as the most prevalent serovars, whereas 42 (5.9%; 95% CI: 4.4%-7.9%) were positive for T gondii, of which 33 samples (78.57%; 95% CI: 64.0%-88.2%) presented a titer of 16, 7 (16.7%; 95% CI: 8.4%-30.7%) a titer of 64, and 1 (2.38%; 95% CI: 0.6%-12.3%) a titer of 256. No significant difference was found among the results obtained and the associated variables such as age and sex.     

Seroprevalence of Sarcocystis neurona and Its Association With Neurologic Disorders in Argentinean Horses

Equine protozoal myeloencephalitis (EPM) is generally caused by Sarcocystis neurona and can produce substantial economic losses on equine production in America. The aims of the present study were to evaluate the seroprevalence of S. neurona in the main horse-production area of Argentina and associate it with the occurrence of neurologic disorders. Serum samples were collected from 640 horses in nine Argentinean provinces. Most of the samples correspond to animals ≥1.5-year-old from different breeds (n = 628); 12 samples were from younger horses. Further seroprevalence comparison was conducted from the older animals grouped with (n = 148) or without neurologic signs (n = 480). Immunoblot: proteins from 2 × 10⁷S. neurona merozoites were used as antigen on each membrane. Reactivity to antigens with relative mobility of 7, 10, and 16 kDa was considered specific for antibodies against S. neurona; reactivity at 30 kDa was recorded separately. The overall seroprevalence for S. neurona was 26.1% (167/640), and all the provinces had positive horses. Seroprevalence of animals with neurologic signs was greater (P < .001) than what was observed in normal horses (39.2% vs. 22.1%), with an odds ratio of 2.27. Reactivity at 30 kDa was detected in 71% of all samples. This study identified a wide distribution of S. neurona–positive animals in Argentina and horses with neurologic signs having a greater seroprevalence than normal horses. Sarcocystis neurona infection should be considered for early differential diagnosis and treatment of animals with neurologic disorders to decrease the economic impact of EPM in Argentina.     

Evidence for widespread Leishmania infantum infection among wild carnivores in L. infantum periendemic northern Spain

Leishmania spp. infection was investigated in tissue samples of wild carnivores from the Spanish Basque Country (BC), by PCR and DNA sequencing. The region is at the northern periphery of Leishmania infantum endemic Iberian Peninsula and infection in the dog (reservoir) or other species has not been previously reported. Leishmania kinetoplast DNA was detected by real-time PCR (rtPCR) in 28% (44/156) of animals. Specifically, in 26% of Eurasian badgers (n = 53), 29% of foxes (n = 48), 29% of stone martens (n = 21) and in 25–50% of less numerous species including genets, wild cats, pole cats, European mink and weasels. Infected animals particularly badgers, were most prevalent in the southernmost province of the BC (Araba) in areas dominated by arable land. Subsequent amplification and sequencing of a fragment of the rRNA internal transcribed spacer 2 (ITS2) from a subset of rtPCR positives samples confirmed the species as L. infantum, showing a high sequence homogeneity with ITS2 sequences of L. infantum from dogs and humans from southern Spain. In summary, this study reports for the first time L. infantum infection in wild carnivores from the BC including in stone martens, pole cats and minks in which infection has not been previously described. It supports the need to study infection in dogs and people in this region and is an example of the value of infection surveillance in wildlife to assess potential risks in the domestic environment and their role in spreading infections in non-endemic areas.     

Epidemiological evaluation of Leishmania infantum zoonotic transmission risk in the recently established endemic area of Northwestern Italy

Leishmania infantum infection had been expanding into new areas due to changes in vector and host biology. Zoonotic visceral leishmaniasis has become endemic in previously unsuitable areas as vectors find favourable climatic conditions and an increasing number of reservoir dogs are moved between traditionally and new endemic areas. Monitoring vector and disease expansion in areas of recent colonization is needed to understand transmission mechanisms and patterns of disease establishment. Here, we studied the infection status of 815 human blood donors and of 803 sympatric dogs from five, newly endemic, areas in Northwestern Italy. In autochthonous dogs, the seroprevalence of anti‐L. infantum antibodies, recorded by Western blot, reached 42.22%, while in humans, the seroprevalence was of 16.81%. No significant correlation between the infection status of dogs and that of their human owners was found, but L. infantum infection was recorded in the different study areas with significant levels of diversity. Restriction fragment length polymorphism showed a high genetic variability of the circulating strains and gave useful insights on patterns of disease establishment into a naïve area.     

Leptospira seroprevalence and associations between seropositivity,clinical disease and host factors in horses

Background

A cross-sectional study was carried out to determine the seroprevalence of different serovars of Leptospira spp. and their association with clinical disease and host factors in Swedish horses.

Methods

Sera from 2017 horses brought to equine clinics during 1997–98 were investigated. The sera were examined by microscopic agglutination test for the presence of antibodies against the following L. interrogans serovars: Bratislava strain Jez, Icterohaemorrhagiae strain Kantorowicz and Pomona strain Pomona and also L. kirschneri sv Grippotyphosa strain Duyster and L. borgpetersenii sv Sejroe strain M 84. Host factors, disease factors, season, pasture access and outdoor confinement variables were analysed with respect to seropositivity to sv Bratislava and Icterohaemorrhagiae. Multivariable logistic regression was used to model seropositivity to sv Bratislava and Icterohaemorrhagiae (seroprevalence > 8%).

Results

The seroprevalence, at a cut-off 1:100, were for sv Bratislava (16.6%), Icterohaemorrhagiae (8.3%), Sejroe (1.2%), Pomona (0.5%) and Grippotyphosa (0.4%). In the multivariable analysis, it was demonstrated that seroprevalence increased with age for sv Bratislava and Icterohaemorrhagiae. For sv Bratislava the seasons April – June and October – December and for sv Icterohaemorrhagiae October – December had higher seroprevalences than other seasons. Horses not used for racing had higher levels of seropositivity to sv Bratislava. Furthermore, horses with respiratory problems as well as horses with fatigue had higher levels of seropositivity to sv Bratislava. Ponies and coldbloods, and horses with access to pasture, had lower seroprevalence for sv Icterohaemorrhagiae. Healthy horses had lower seroprevalence for sv Icterohaemorrhagiae, than non-healthy horses.

Conclusion

There was no significant association between clinical signs and disease and positive titres to sv Bratislava (except for the association between respiratory problems and fatigue and seropositivity to sv Bratislava). The results suggest that horses with increasing age and exposed to factors associated with outdoor life had an increased seroprevalence for sv Bratislava, indicating that horses get infected from outdoor and/or are exposed to shedding from other horses (management dependent). For sv Icterohaemorrhagiae, management possibly plays a role as ponies and coldbloods as well as healthy horses had lower seroprevalence. Overall, the age of the horse should be taken into consideration when evaluating the titre as the average healthy horse has a higher titre than a young horse.     

Diagnosis of Equine Protozoal Myeloencephalitis Using Indirect Fluorescent Antibody Testing and Enzyme-Linked Immunosorbent Assay Titer Ratios for Sarcocystis neurona and Neospora hughesi

The aim of this study was to compare two serologic tests used to support a diagnosis of equine protozoal myeloencephalitis (EPM). Serum and cerebrospinal fluid (CSF) samples were analyzed for antibodies to Sarcocystis neurona and Neospora hughesi by indirect fluorescent antibody testing (IFAT) and surface antigens of S. neurona and N. hughesi by enzyme-linked immunosorbent assay (ELISA). The samples originated from neurologic horses with confirmed and suspected EPM (nine S. neurona, three N. hughesi), from neurologic horses with confirmed neurologic diseases other than EPM (16 horses) and from healthy horses (10). The IFAT on CSF and ELISA titer ratios showed equal sensitivity in diagnosing EPM caused by S. neurona. The ELISA titer ratios showed slightly greater specificity in diagnosing EPM than the IFAT on CSF. Overall agreement between the IFAT on CSF and ELISA titer ratio was 90.9%. The IFAT on CSF and ELISA serum/CSF ratio are indicated to help support a laboratory diagnosis of EPM.     

Seroprevalence and risk factors associated with Babesia caballi and Theileria equi infection in equids

A cross-sectional study was carried out on equids (horses, mules and donkeys) in Andalusia, Southern Spain, to assess the level of exposure to equine piroplasmosis and to investigate risk factors associated with these infections. At least one animal seropositive for Theileria equi and/or Babesia caballi was detected in 222/380 (58.4%) herds sampled by competitive inhibition ELISAs. The seroprevalences for B. caballi and T. equi were 13.2% and 56.1%, respectively; there was serological evidence of co-circulation of both piroplasms in 10.8% of herds. Antibodies against equine piroplasms were detected in 286/537 (53.3%) animals; 61 (11.4%) were seropositive for B. caballi, 270 (50.3%) were seropositive for T. equi and 24 (8.4%) were seropositive for both T. equi and B. caballi.There was a significantly higher seroprevalence of B. caballi in mules (32.1%) compared with donkeys (17.0%) and horses (7.9%), and a significantly higher seroprevalence of T. equi in mules (66.1%) in comparison with horses (48.6%), but not donkeys (47.2%). There were significant differences in prevalence of both piroplasms among locations; the seroprevalence of B. caballi ranged from 0 to 22.5%, while the seropositivity to T. equi ranged from 26.7 to 63.3%. A multiple logistic regression model indicated that the risk factors associated with a higher T. equi seroprevalence were increased age, presence of ticks and vaccination against other diseases. Risk factors associated with a higher seroprevalence of B. caballi were species (mules compared to horses), entry of horses in the last 6 months, presence of ticks and presence of shelter. The findings indicate widespread exposure to equine piroplasmosis in Southern Spain.     

Retrospective Study on Seroprevalence of Borrelia burgdorferi Antibodies in Horses in Minnesota

To determine the seroprevalence of Borrelia burgdorferi antibodies in horses in Minnesota, the database of the Veterinary Diagnostic Laboratory, University of Minnesota, was searched over a 10-year period (May 2001 to May 2010). A total of 1,260 equine serum samples submitted by 112 veterinary clinics were tested using an indirect fluorescent antibody test. Samples with titers of ≥1:320 were considered positive. The average rate of seroprevalence was 58.7%, indicating high exposure of horses to B burgdorferi in Minnesota. Our results indicate that borreliosis should be considered as a differential in cases of horses with undiagnosed musculoskeletal or neurologic disease.     

Seroprevalence of Neospora,Toxoplasma gondii and Sarcocystis neurona antibodies in horses from Jeju island,South Korea

Parasite-specific antibody responses to Neospora spp. and Toxoplasma gondii, antigens were detected using the indirect fluorescent antibody test (IFAT) and immunoblot analysis in a korean equine population located on Jeju island, South Korea (126 degrees 12' E and 33 degrees 34' N). For comparison, a naturally infected Neospora hughesi horse and an experimentally inoculated T. gondii equid (pony) were used. In addition, all samples were tested for antibodies to Sarcocystis neurona by immunoblot analysis. A total of 191 serum samples from clinically normal horses were evaluated. Only 2% (4 out of 191) and 2.6% (5 out of 191) of the samples had showed reactivity at 1:100 using the IFAT for Neospora spp. and T. gondii, respectively. For T. gondii, two samples matched the antigen banding pattern of the positive control by immunoblot analysis. No sample was positive for N. hughesi by immunoblot analysis in this study. Overall, there was a 1% seroprevalence for T. gondii antibodies in the horses tested based on immunoblot analysis. The seroprevalence for S. neurona and N. hughesi antibodies was 0%. We concluded that these horses are either not routinely exposed to these parasites or antibody titers are not sufficiently elevated to be detectable. It is most likely the former explanation since Jeju island equine farms are isolated from the main land, and the horses were all less than 3 years of age. This na?ve population of horses could be useful when evaluating S. neurona serodiagnostic tests or evaluating potential S. neurona vaccines since exposure risks to S. neurona and closely related parasites are negligible.     

Equine Piroplasmosis

Equine piroplasmosis (EP) is a tick-borne protozoal disease of horses, mules, donkeys, and zebras that is characterized by acute hemolytic anemia. The etiologic agents are two hemoprotozoan parasites, Theileria equi (Laveran, 1901) and Babesia caballi (Nutall and Strickland, 1910) that are transmitted primarily by ixodid ticks. Equine piroplasmosis is found globally where tick vectors are present and is endemic in tropical, subtropical, and some temperate regions. Horses infected with B. equi remain seropositive for life; horses infected with B. caballi are seropositive for several years to life. Economic losses associated with EP are significant and include the cost of treatment, especially in acutely infected horses; abortions; loss of performance; death; and restrictions in meeting international requirements related to exportation or participation in equestrian sporting events. Equine babesiosis–free countries limit the entrance of Babesia-seropositive horses into their countries. In the United States a few sporadic outbreaks have occurred in recent years but have been limited due to implementation of stringent control methods. The cELISA for both T. equi and B. caballi is currently the recommended test for international horse transport. Different therapies for control and sterilization of the parasites are discussed.     

Leishmania infantum in wild animals in endemic areas of southern Italy

Leishmania infantum infection in wildlife is increasingly reported in Europe, but scant data are available in Italy so far. This study aimed to investigate the circulation of L. infantum among sylvatic hosts in Sicily (southern Italy), a highly endemic area for canine leishmaniosis, through serological and molecular tools. Target tissues (skin, spleen, lymph nodes) collected from 71 European rabbits, 2 European hares, 7 red foxes, 11 European wildcats and 1 pine marten, were qPCR analysed for the detection of L. infantum DNA. Additionally, 40 rabbits, older than one year, were serologically screened for specific anti-Leishmania antibodies. Leishmania infantum was molecularly diagnosed in 5.4% (n = 5) of the examined animals (3/71 European rabbits, 2/7 red foxes). In many of the qPCR positive animals (4/5), the parasite DNA was more prevalent in visceral than cutaneous tissues. None of the positive animal showed signs of disease and/or macroscopic alterations of organs; low parasitic burden in all positive tissue samples was also recorded. Only one rabbit serum (i.e., 2.5%) tested positive for anti-Leishmania antibodies. The seropositive rabbit was in good health status and no amastigotes were observed in lymph-node aspirate and blood smears.This study provides first evidence of L. infantum infection in wild animals from Sicily (southern Italy). Despite the low prevalence of infection here reported, the circulation of the Leishmania in wild reservoirs in Sicily remains worthy of future investigations for a better understanding of their role in the epidemiology of the disease as well as to fine-tune control strategies in the area.     

Seroprevalence of Toxoplasma gondii in free-ranging wild boars hunted for human consumption in Estonia

Background

Although the prevalence of human Toxoplasma gondii infections is high in Estonia, no information is available on the prevalence of infections in the local animal populations. Wild boars are a good indicator species for estimating the prevalence and spread of T. gondii and were thus investigated in this nationwide cross-sectional study. Volunteer hunters sampled cardiac or skeletal muscle of 471 wild boars legally hunted for human consumption in Estonia during the hunting season of 2012–2013. Serosanguineous meat juice samples were obtained from thawed tissue samples, diluted 1:40, and screened for specific anti-T. gondii IgG antibodies with a commercial direct agglutination test.

Results

Almost one-quarter (113; 24%) of the wild boars examined were seropositive for T. gondii. The seroprevalence did not differ significantly between age groups or sexes. The seroprevalence was lowest in Viljandimaa, which is located in the southern part of Estonia. In other counties, the infection was evenly prevalent.

Conclusions

In Estonia, wild boars are commonly exposed to T. gondii, which is endemic and widespread. The consumption of raw or undercooked meat of Estonian wild boars may pose an infection risk to humans and other hosts.     

A systematic review of the efficacy of prophylactic control measures for naturally-occurring canine leishmaniosis,part I: Vaccinations

Canine leishmaniosis (CanL) is an important zoonotic disease; however, the efficacy of available vaccines for the prevention of naturally-occurring Leishmania infantum (L. infantum) infection in dogs remains unclear.     

Evidence of Toxoplasma gondii Exposure among Horses in Korea

The present study investigated the seroprevalence of Toxoplasma gondii (T. gondii) antibodies by ELISA in horses reared in Korea. Serum samples were collected from 2009 through 2013 from 816 horses reared in Korea. Analysis was performed using a commercial toxoplasmosis ELISA kit to detect anti-T. gondii antibodies. Overall, 24 out of 816 horses (2.9%) were seropositive for T. gondii. The result was analyzed by age, gender, breed and region. Significant differences were observed according to breed and region (P<0.05). This is the first nationwide serological investigation of T. gondii in horses reared in Korea. The study results reveal that T. gondii occurs nationwide in Korean horses.     

Leishmania infantum in a Central Italy dog shelter: Retrospective study of serologic reactivity during a 4-year period in a confined dog population subjected to preventive and therapeutic treatment

Leishmaniasis from Leishmania infantum is a parasitary zoonotic disease and a serious problem to public health. Guidelines from Italian Health Authority (Istituto Superiore di Sanità) suggest to control the zoonotic visceral leishmaniasis canine reservoir in endemic areas using an association of preventive and therapeutic tools. Moreover, in literature there are no studies about the long term effects on the disease seroprevalence and incidence in relation to this “holistic” approach. Past research has considered the effects of the alternative employment of preventive or therapeutic treatment, usually for limited periods. In this retrospective study the patterns of seroprevalence and incidence of leishmaniasis in a dog shelter sited in an endemic area of Central Italy are described throughout a 4-year period. Both preventive spot-on tools (imidacloprid/permetrin) and therapeutic protocols based on antimonials and allopurinol were administered. The results showed a progressive reduction of prevalence and incidence of serological reactivity to L. infantum, corroborating the effectiveness of the treatment administered to the animals. Significant improvements from the beginning to the end of the 4-year period were reported, considering both prevalence and incidence. A very low rate of relapses (8% in a pool of 67 subjects positive since 2004; 10.2% among all subjects enrolled in the study) was achieved.     

Cutaneous immune mechanisms in canine leishmaniosis due to Leishmania infantum

Canine leishmaniosis (CanL) caused by the parasite Leishmania infantum is a systemic disease with variable clinical signs. The disease is endemic in the Mediterranean countries and dogs are the main domestic reservoir of the parasite. The quite complicated immune response against the parasite is crucial for the evolution of CanL infection with the skin playing a major role in its immunopathogenesis.After the inoculation of Leishmania promastigotes into the dermis by sand fly bites, complement factors, Langerhan's cells, neutrophils, fibroblasts and keratinocytes are involved in the activation of the innate arm of the skin immune system, with the macrophages and dendritic cells to play a major key role.The effective activation of cellular immunity is the cornerstone of dog's resistance against the parasite. Promastigotes reaching the dermis are engulfed, processed and transferred by APCs to draining lymph nodes to stimulate naïve T-cells for proliferation and differentiation into armed effector T-cells. Th1 cells activate the infected macrophages to kill Leishmania, whereas Th2 cells divert the immune response to humoral immunity and down regulation of cellular immunity with Th1 cell anergy. Inhibition of co-stimulatory molecules expression by infected macrophages contributes to T-cell anergy. In canine subclinical infections cutaneous lymphocytic infiltrate and parasites are absent, as opposed to dogs with clinical leishmaniosis. CD8+ cells constitute a significant population of cellular immunity in CanL since they outnumber CD4+ cells in the dermis, producing IFN-γ in sub clinically infected dogs and high levels of IL-4 in dogs with clinical leishmaniosis.Numerous B-lymphocytes have been shown to heavily infiltrate the dermis at least in exfoliative dermatitis in CanL. A mixed Th1/Th2 cytokine profile has been found in the dermis of naturally infected with L. infantum dogs. In the skin of dogs with clinical leishmaniosis, where plasma cells outnumber T lymphocytes in the dermal infiltrate, there is an overproduction of IL-4, IL-13 and TNF-α leading to Th2-biased humoral immune response. The issue of humoral immunity polarization in CanL remains controversial. Much still needs to be learned about other mechanisms underlying the complex interaction between the skin immune system and the parasite.     

Latitudinal variability in the seroprevalence of antibodies against Toxoplasma gondii in non-migrant and Arctic migratory geese

Toxoplasma gondii is an intracellular coccidian parasite found worldwide and is known to infect virtually all warm-blooded animals. It requires a cat (family Felidae) to complete its full life cycle. Despite the absence of wild felids on the Arctic archipelago of Svalbard, T. gondii has been found in resident predators such as the arctic fox and polar bear. It has therefore been suggested that T. gondii may enter this ecosystem via migratory birds. The objective of this study was to identify locations where goose populations may become infected with T. gondii, and to investigate the dynamics of T. gondii specific antibodies. Single blood samples of both adults and juveniles were collected from selected goose species (Anser anser, A. brachyrhynchus, Branta canadensis, B. leucopsis) at Arctic brood-rearing areas in Russia and on Svalbard, and temperate wintering grounds in the Netherlands and Denmark (migratory populations) as well as temperate brood-rearing grounds (the Netherlands, non-migratory populations). A modified agglutination test was used on serum, for detection of antibodies against T. gondii. Occasional repeated annual sampling of individual adults was performed to determine the antibody dynamics. Adults were found seropositive at all locations (Arctic and temperate, brood-rearing and wintering grounds) with low seroprevalence in brood-rearing birds on temperate grounds. As no juvenile geese were found seropositive at any brood-rearing location, but nine month old geese were found seropositive during spring migration we conclude that geese, irrespective of species and migration, encounter T. gondii infection in wintering areas. In re-sampled birds on Svalbard significant seroreversion was observed, with 42% of seropositive adults showing no detectable antibodies after 12 months, while the proportion of seroconversion was only 3%. Modelled variation of seroprevalence with field data on antibody longevity and parasite transmission suggests seroprevalence of a population within a range of 5.2–19.9%, in line with measured values. The high occurrence of seroreversion compared to the low occurrence of seroconversion hampers analysis of species- or site-specific patterns, but explains the absence of an increase in seroprevalence with age and the observed variation in antibody titre. These findings imply that even though infection rate is low, adults introduce T. gondii to the high Arctic ecosystem following infection in temperate regions.