The Zoonotic Parasite Dirofilaria repens Emerged in the Baltic Countries Estonia, Latvia, and Lithuania in 2008-2012 and Became Established and Endemic in a Decade.

The zoonotic parasite Dirofilaria repens has spread toward north in Europe, and cases of autochthonous dirofilariosis caused by D. repens have emerged in the Baltic countries Estonia, Latvia, and Lithuania. We conducted a review on the emergence of dirofilariosis in humans and domestic dogs in these three countries in northeastern Europe. Based on the available literature and reports, the first finding in the Baltic countries was made in Latvia in 2008, followed by the first in Lithuania in 2010, and the first in Estonia in 2012. In all three countries, further findings were reported soon after the first reports. By the end of 2019, autochthonous human D. repens infections had been described from Latvia and Lithuania, and autochthonous canine D. repens infections had been described from all three Baltic countries. While no epidemiological studies estimating prevalence or incidence of the human infections have been published from the three countries, a substantial proportion of investigated dogs have tested positive for microfilariae in studies performed in Latvia and Lithuania. Dirofilariosis is an emerging zoonosis in northern Europe, and the summarized data confirm that D. repens has become established and endemic in the Baltic countries. The available data do not provide a good overview of the situation, and further epidemiological studies are needed. Awareness about the recently emerged zoonotic parasite should be increased among medical doctors, veterinarians, and the general public. Managing this zoonotic infection is a public health challenge that needs to be addressed using a One Health approach. Investigating the spread of D. repens in the Baltic countries could be useful for better preparedness for the anticipated further spread to the Nordic countries.

Habitat quality affects stress responses and survival in a bird wintering under extremely low ambient temperatures.

Animals normally respond to stressful environmental stimuli by releasing glucocorticoid hormones. We investigated whether baseline corticosterone (CORT), handling-induced corticosterone concentration(s), and body condition indices of members of willow tit (Poecile montanus) groups differed while wintering in old growth forests and managed young forests in mild weather conditions and during cold spells. Willow tits spend the winter season in non-kin groups in which dominant individuals typically claim their priority to access resources, while subordinate individuals may experience greater levels of stress and higher mortality, especially during cold spells. We captured birds to measure baseline CORT and levels of handling-induced CORT secretion after 20 min of capture. Willow tits in the young forests had higher baseline CORT and a smaller increase in CORT in response to capture than individuals in the old forests. Baseline CORT was higher in females and juvenile birds compared to adult males, whereas handling-induced CORT secretion did not differ between birds of different ages. During cold spells, baseline CORT of willow tits increased and handling-induced CORT secretion decreased, especially in birds in young forests. Willow tits' survival was higher in the old forests, with dominant individuals surviving better than subordinates. Our results show that changes in CORT secretion reflect responses to habitat quality and climate harshness, indicating young managed coniferous forests as a suboptimal habitat for the willow tit.

Autochthonous canine babesiosis caused by Babesia canis canis in Latvia.

This is the first report of confirmed canine babesiosis in Latvia supporting the observed geographical expansion of this disease. Between 2009 and 2011 three dogs which have not traveled outside of Latvia were diagnosed with babesiosis. Hematological analysis and serological tests for granulocytic anaplasmosis, ehrlichiosis and borreliosis were negative (Idexx SNAP 4Dx test). Peripheral blood erythrocytes of the three dogs contained large Babesia that were identified as Babesia canis canis by PCR. Sequences of partial 18S rRNA gene were 98-100% similar to the sequences of B. canis canis isolated from dogs in other European countries. We conclude that these are the first autochthonous canine babesiosis cases reported from Latvia.

Nocturnal loss of body reserves reveals high survival risk for subordinate great tits wintering at extremely low ambient temperatures.

Winter acclimatization in birds is a complex of several strategies based on metabolic adjustment accompanied by long-term management of resources such as fattening. However, wintering birds often maintain fat reserves below their physiological capacity, suggesting a cost involved with excessive levels of reserves. We studied body reserves of roosting great tits in relation to their dominance status under two contrasting temperature regimes to see whether individuals are capable of optimizing their survival strategies under extreme environmental conditions. We predicted less pronounced loss of body mass and body condition and lower rates of overnight mortality in dominant great tits at both mild and extremely low ambient temperatures, when ambient temperature dropped down to -43 °C. The results showed that dominant great tits consistently maintained lower reserve levels than subordinates regardless of ambient temperature. However, dominants responded to the rising risk of starvation under low temperatures by increasing their body reserves, whereas subdominant birds decreased reserve levels in harsh conditions. Yet, their losses of body mass and body reserves were always lower than in subordinate birds. None of the dominant great tits were found dead, while five young females and one adult female were found dead in nest boxes during cold spells when ambient temperatures dropped down to -43 °C. The dead great tits lost up to 23.83 % of their evening body mass during cold nights while surviving individuals lost on average 12.78 % of their evening body mass. Our results show that fattening strategies of great tits reflect an adaptive role of winter fattening which is sensitive to changes in ambient temperatures and differs among individuals of different social ranks.

Heterophil/lymphocyte ratios predict the magnitude of humoral immune response to a novel antigen in great tits (Parus major).

Animals display remarkable individual variation in their capacity to mount immune responses against novel antigens. According to the life-history theory, this variation is caused by the costs of immune responses to the hosts. We studied one of such potential costs, depletion of somatic resources in wintering wild-caught captive passerines, the great tits (Parus major) by immune challenging the birds with a novel antigen, killed Brucella abortus (BA) suspension. We found that despite mild temperature conditions in captivity and ad libitum availability of food, immune challenge depleted somatic resources (as indicated by a body mass loss) and elevated relative proportion of heterophils to lymphocytes (H/L ratio) in the peripheral blood of birds. However, body mass loss did not covary with an increase in H/L ratios between two sampling events, which indicates that these two markers of health state describe different aspects of individual physiological condition. Antibody titres were not associated with the extent of body mass loss during the development of immune response, which shows that the somatic cost of immune response was not proportional to the amount of antibody produced. Birds with high pre-immunisation H/L ratios mounted weaker antibody response, which is indicative of stress-induced suppression of humoral immune response and is consistent with the concept of an antagonistic cross-regulation between different components of the immune system. The latter finding suggests a novel diagnostic value of H/L ratios, which reinforces the utility of this simple haematological index for prediction of the outcomes of complicated immune processes.