Serological testing of Schmallenberg virus in Swedish wild cervids from 2012 to 2016.

BACKGROUND: Schmallenberg virus (SBV) first emerged in Europe in 2011, and in Sweden in late 2012. The virus was still circulating in parts of Europe in 2015. In recent testing, the virus has not been detected in Swedish domestic animals, indicating that it is no longer circulating in Sweden. It is not known if the virus has circulated and is still circulating in Swedish wild cervid populations and whether wildlife can act as virus reservoirs. The aim of this study was to investigate whether SBV has circulated, and is still circulating among wild cervids in Sweden. RESULTS: Ninety-two sera from moose (Alces alces, n = 22), red deer (Cervus elaphus, n = 15), fallow deer (Dama dama, n = 44), and roe deer (Capreolus capreolus, n = 11) were collected and analyzed for antibodies against SBV. The sampling occurred in the southern and middle part of Sweden during three time periods: 1) before the vector season in 2012, 2) after the vector season in 2012, and 3) after the vector season in 2015. Animals from periods 1 and 2 were of varying ages, whereas animals collected in period 3 were born after the vector season 2013. Animals from period 1 (n = 15) and 3 (n = 47) were seronegative, but, 53% (16 of 30) of animals from period 2 were seropositive, determined by SBV competitive ELISA. Samples from period 2 were additionally analyzed for SBV-neutralizing antibodies. Such antibodies were detected in 16/16 SBV-N-antibody-positive, 3/12 negative and 2/2 doubtful sera. The two tests were in accordance at SBV-neutralizing antibody titers of 1:32 or higher. CONCLUSION: Our results show that SBV circulated among wild cervids during the vector season of 2012. Three years later, no SBV-antibodies were detected in animals born after the vector season 2013. The likely absence of SBV circulation in Sweden, in contrast to other parts of Europe, might be explained by the annual occurrence of a vector-free season due to climate conditions. Interpretations are limited by the small sample-size, but the results suggest that the SBV competitive ELISA has high specificity but might have slightly lower sensitivity compared to a seroneutralization assay, when using samples from wild cervids.

Temporal and spatial variation in Anaplasma phagocytophilum infection in Swedish moose (Alces alces).

SUMMARY: 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.

Seroprevalence of Neospora caninum in gray wolves in Scandinavia.

Transmission of the protozoan parasite Neospora caninum between wild and domestic animals has gained some interest during recent years. Because of the close relationship between gray wolf (Canis lupus) and dog it has been suggested that gray wolf is a definitive host for the parasite. The aim of this study was to estimate the seroprevalence of N. caninum in Scandinavian gray wolves and to investigate any geographical patterns of the infection. The investigation was based on blood samples collected from 109 wolves between 1998 and 2009 within the Scandinavian wolf project Skandulv. They were analysed by N. caninum iscom ELISA and those with absorbance values exceeding 0.20 were also analysed by immunoblotting. Samples that were positive in both tests were deemed positive. Four (3.7%) wolves were positive at the first sampling. They were all sampled 2005 at different locations, and were both females and males. From one male wolf three samples were collected over a 7-year period. No antibodies were detected at the first sampling in 1998 when he was approximately 8 months old but when he was sampled again 5 and 7 years later the ELISA and immunoblotting were positive. The results indicate that N. caninum infection is present in Scandinavian wolves. It is unclear how the wolves acquired the infection.

Changes in segmental reflexes following chronic spinal cord hemisection in the cat. I. Increased monosynaptic and polysynaptic ventral root discharges.

The effect of a chronic spinal cord hemisection on segmental reflex transmission was studied in cats. Recordings of ventral root responses were made after a terminal transection below the initial lesion to eliminate descending influence through the intact spinal half. Procedures to ensure comparability between sides, that are lacking in earlier work on this experimental model, were introduced in the present work. It was demonstrated that there was an increase in reflex size on the lesioned (left) side, relative to the other side, of both mono- and polysynaptic reflexes. The reflex changes were found at all survival times studied (from 2 to 515 days). In control animals mono- and polysynaptic reflexes were found to be larger on the right side. It is discussed that side symmetry of reflex size is not to be presupposed even in a normal population. Detailed clinical examinations of lesioned animals were not performed, but a tendency for enhancement of the ipsilateral knee-jerk was found. There was no syndrome of spasticity and general motor recovery was very good.

Changes in segmental reflexes following chronic spinal cord hemisection in the cat. II. Conditioned monosynaptic test reflexes.

In a companion paper (Hultborn & Malmsten 1983) it was described that ventral root discharges to stimulation of peripheral nerves became larger on the side of a chronic spinal hemisection (left) than on the other side. In the present paper, based on the same experiments, conditioning of monosynaptic test reflexes was used to study changes of both excitatory and inhibitory effects on specified motoneuronal pools. Conditioning stimulation was given to IA afferents (reciprocal Ia inhibition, presynaptic inhibition of Ia fibers), high threshold muscle afferents, low and high threshold cutaneous afferents and motor axons (recurrent inhibition). A comparison of the efficacy of conditioning stimuli on the two sides showed that facilitatory effects were larger on the side of hemisection in a clear majority of cases. Inhibition was almost always either more efficient on the side of hemisection or equally efficient on the two sides. In control cats, facilitatory effects tended to be larger on the right side, while the results for inhibitory conditioning generally showed no clear side-bias. The increase in facilitatory effects after lesions may contribute to symptoms of spasticity.

Time course of segmental reflex changes after chronic spinal cord hemisection in the rat.

In a companion paper (Hultborn & Malmsten 1983 a) it was described that, in the cat, direct excitatory reflexes became larger on the side of a chronic spinal hemisection than on the other side. In this paper the time course for change of the size of excitatory reflexes after spinal cord hemisection in the rat is described. Ipsilateral reflexes obtained by stimulation of cut dorsal roots L 4 and L 5 were recorded in the corresponding cut ventral roots. It was found that reflexes became larger on the lesioned (left) side than on the opposite side. For both mono- and polysynaptic reflexes there was a marked peak in left/right ratio on reflex size at 2 to 6 days post lesion. The ratio then returned to normal but increased again from about 21 days until at least 135 days. In control rats reflexes were larger on the right side, in agreement with findings in the cat.

Effects of chronic partial deafferentiation on the electrical properties of lumbar alpha-motoneurones in the cat.

Membrane properties of cat spinal alpha-motoneurones were compared in cats following acute and chronic low (L5) spinal section and dorsal rhizotomy (L7--S1) and in cats with intact spinal cord in order to investigate effects of chronic partial deafferentation. The most significant change observed was a decrease in electrotonic length of the chronically deafferented neurones. Calculations showed that this decrease was related to a 15--20% reduction in length of an equivalent cylinder used to represent a motoneurone. Using a compartmental model, calculations showed that the peak voltage produced by a given synaptic input would be increased by 6--36% by chronic section. Such an increase is not sufficient to explain reported increases in EPSP peak amplitudes. Neither peak amplitude (and underlying conductance change) nor duration of the afterhyperpolarizaton were affected by the acute or chronic sections. No obvious changes in the delayed depolarization were observed. The properties of the repetitive discharge induced by intracellular current injection was not altered by chronic section.