Estimated specific antibody-based true sero-prevalences of canine filariosis in dogs in Central Europe and the UK

Abstract

Dirofilariosis is a vector-borne disease mainly caused by Dirofilaria immitis and Dirofilaria repens. In contrast to the known endemicity of dirofilariosis in southern and south-eastern Europe, information on the distribution of D. repens in Central-Europe is fragmentary. We tested 8877 serum samples from dogs from Austria, Denmark, Germany, Italy, Lithuania, Poland, Switzerland and the UK using an ELISA detecting filarial-specific antibodies, hypothesising higher occurrence of D. repens. Based on two overlapping frequency distributions, presumed negative samples had a mean optical density (OD) value of 0.097, representing 97.45% of all samples. Presumed positive samples, representing 2.55% of all sera, had a mean OD value of 0.287. Test prevalence based on the calculated cut-off was 3.51% for all sera (4.36% for Austria, 1.94% for Denmark, 1.39% for Germany, 3.37% for Italy, 6.90% for Lithuania, 6.99% for Poland, 0.77% for Switzerland and 0.0% for the UK, respectively). The bimodal distribution, representing overlapping distributions of OD values from positive and negative dogs, enabled the assignment of a probability of true infection status to each dog. Mean probabilities of true infection status across groups, based on the postal codes of origin, allowed us to estimate and map true prevalences. For all countries, except the UK, the true prevalence was lower than the test prevalence. The large number of serum samples and the use of a non-gold standard analytical method allowed us to create a more realistic picture of the distribution of D. repens in Central Europe and the UK.

The long-distance relationship between Dirofilaria and the UK: case report and literature review

“…Thus, pets travelling from or to the United Kingdom may be subject to differing health requirements compared to EU countries ( 54 , 55 ). During the first epidemiological survey conducted in 2010, the filarial-specific antibody prevalence was recorded as 0% over a total of 1,028 dogs tested across the United Kingdom ( 56 ). A later European study performed between 2016 and 2020 revealed a canine HW seroprevalence of 5–7% in central/southern England, with no seropositive dogs detected in other parts of the country ( 57 ).…”

“…A later European study performed between 2016 and 2020 revealed a canine HW seroprevalence of 5–7% in central/southern England, with no seropositive dogs detected in other parts of the country ( 57 ). While the overall seroprevalence of HW infection remains very low ( 56 , 57 ), there have been two reports of clinical D. repens infection in United Kingdom dogs in recent years in the midlands of England ( 12 , 58 , 59 ). Both studies reported infection in imported dogs, the first originating from Romania ( 59 , 60 ) and the second from Corfu ( 58 ).…”

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“…Both bacteria infect the tick through the feeding [7] and can infect new subjects when ticks molt and bite again a new host or pass to a new tick generation by trans-ovarian transmission. Dirofilaria immitis is one nematode transmitted by several species [8] of mosquitoes [9] from genera Culex, Aedes, Anopheles and Ochlerotatus. All filaria have filiform elongated body.…”