Babesia divergens becoming extinct in cattle of Northeast Hungary: new data on the past and present situation

Endemisation and management of Babesia divergens on a beef production farm

The hard tick Ixodes ricinus transmits a variety of zoonotic pathogens, including Babesia divergens, the most common cause of bovine babesiosis in northern Europe. In endemic areas, cattle are rarely clinically affected, as animals up to the age of nine months are resistant against relevant clinical disease and develop protective premunity. However, outbreaks in immunologically naïve herds may lead to considerable losses. Such an outbreak with a high mortality rate occurred in 2018 on a northern German beef production farm, as previously reported. The present study provides an update on the epidemiological situation and management strategy of the farm. In spring 2022, blood samples were taken from 46 animals for PCR and serological testing before pasture turnout. Although no clinical cases had been noticed since 2019, B. divergens DNA was detected by quantitative real-time PCR (qPCR), followed by amplification and sequencing of the 18S rRNA gene, in 6.5% (3/46) of cattle blood samples. Presence of anti-B. divergens antibodies was confirmed in 26.1% (12/46) of animals, while further 10.9% (5/46) had a borderline antibody titre. The antibody status of 23 of these animals had already been determined in 2018 and/or 2020, revealing fluctuating titre patterns indicative of repeated pathogen exposure. Moreover, 457 questing I. ricinus specimens collected on the farm's pastures and 83 I. ricinus specimens detached from cattle were screened for Babesia spp. DNA by qPCR, followed by 18S rDNA amplification and sequencing. Endemisation of B. divergens was confirmed by 0.9% (4/457) positive questing I. ricinus, while the ticks detached from cattle were Babesia-negative. The farm's management strategy includes annual metaphylactic treatment with imidocarb dipropionate during the main tick exposure period in spring. However, the antibody titre fluctuations and the persistent infections at the end of the housing period indicate that the absence of clinical disease is primarily due to a rising level of premunity. Metaphylactic treatment with imidocarb seems to be a suitable management option to protect newly acquired immunologically naïve animals. The endemisation of B. divergens is also of public health significance, as the pastures are located close to a tourist destination in a popular hiking area.

Babesiosis in Southeastern, Central and Northeastern Europe: An Emerging and Re-Emerging Tick-Borne Disease of Humans and Animals

There is now considerable evidence that in Europe, babesiosis is an emerging infectious disease, with some of the causative species spreading as a consequence of the increasing range of their tick vector hosts. In this review, we summarize both the historic records and recent findings on the occurrence and incidence of babesiosis in 20 European countries located in southeastern Europe (Bosnia and Herzegovina, Croatia, and Serbia), central Europe (Austria, the Czech Republic, Germany, Hungary, Luxembourg, Poland, Slovakia, Slovenia, and Switzerland), and northern and northeastern Europe (Lithuania, Latvia, Estonia, Iceland, Denmark, Finland, Sweden, and Norway), identified in humans and selected species of domesticated animals (cats, dogs, horses, and cattle). Recorded cases of human babesiosis are still rare, but their number is expected to rise in the coming years. This is because of the widespread and longer seasonal activity of Ixodes ricinus as a result of climate change and because of the more extensive use of better molecular diagnostic methods. Bovine babesiosis has a re-emerging potential because of the likely loss of herd immunity, while canine babesiosis is rapidly expanding in central and northeastern Europe, its occurrence correlating with the rapid, successful expansion of the ornate dog tick (Dermacentor reticulatus) populations in Europe. Taken together, our analysis of the available reports shows clear evidence of an increasing annual incidence of babesiosis across Europe in both humans and animals that is changing in line with similar increases in the incidence of other tick-borne diseases. This situation is of major concern, and we recommend more extensive and frequent, standardized monitoring using a "One Health" approach.

Zoonotic Tick-Borne Pathogens in Temperate and Cold Regions of Europe-A Review on the Prevalence in Domestic Animals

Ticks transmit a variety of pathogens affecting both human and animal health. In temperate and cold regions of Europe (Western, Central, Eastern, and Northern Europe), the most relevant zoonotic tick-borne pathogens are tick-borne encephalitis virus (TBEV), Borrelia spp. and Anaplasma phagocytophilum. More rarely, Rickettsia spp., Neoehrlichia mikurensis, and zoonotic Babesia spp. are identified as a cause of human disease. Domestic animals may also be clinically affected by these pathogens, and, furthermore, can be regarded as sentinel hosts for their occurrence in a certain area, or even play a role as reservoirs or amplifying hosts. For example, viraemic ruminants may transmit TBEV to humans via raw milk products. This review summarizes the role of domestic animals, including ruminants, horses, dogs, and cats, in the ecology of TBEV, Borrelia spp., A. phagocytophilum, Rickettsia spp., N. mikurensis, and zoonotic Babesia species. It gives an overview on the (sero-)prevalence of these infectious agents in domestic animals in temperate/cold regions of Europe, based on 148 individual prevalence studies. Meta-analyses of seroprevalence in asymptomatic animals estimated an overall seroprevalence of 2.7% for TBEV, 12.9% for Borrelia burgdorferi sensu lato (s.l.), 16.2% for A. phagocytophilum and 7.4% for Babesia divergens, with a high level of heterogeneity. Subgroup analyses with regard to animal species, diagnostic test, geographical region and decade of sampling were mostly non-significant, with the exception of significantly lower B. burgdorferi s.l. seroprevalences in dogs than in horses and cattle. More surveillance studies employing highly sensitive and specific test methods and including hitherto non-investigated regions are needed to determine if and how global changes in terms of climate, land use, agricultural practices and human behavior impact the frequency of zoonotic tick-borne pathogens in domestic animals.

Emergence and Epidemiology of Bovine Babesiosis Due to Babesia divergens on a Northern German Beef Production Farm

Babesia divergens, transmitted by the tick Ixodes ricinus, is the most common cause of bovine babesiosis in northern Europe and plays a role as a zoonotic pathogen. However, several studies have indicated a decline of B. divergens prevalence in Europe during the last decades. Here, we investigate the epidemiology of bovine babesiosis on a beef production farm in northern Germany, which had not been affected by babesiosis until an initial outbreak in 2018. In June 2018, 21 adult cattle died, showing classical symptoms of babesiosis. Babesia divergens merozoites were detected in blood smears of clinically affected animals and the species was confirmed by PCR and sequencing of a part of the 18S rRNA gene. In 2018, screening of the farm's entire stock by PCR revealed that Babesia-positive animals were present in only one of five herds grazing on different pastures. In the following year, further babesiosis cases occurred in multiple herds. In March 2020, 95 cattle were tested for anti-B. divergens antibodies and 36 of them (37.89%) had positive titres. To investigate the local Babesia prevalence in ticks, 1,430 questing I. ricinus ticks (555 larvae, 648 nymphs, 227 adults) were collected on the farm's pastures and subjected to PCR for Babesia detection. Babesia divergens DNA could not be detected, but Babesia microti showed an overall prevalence of 0.49% (7/1,430; 0.88% [2/227] of adult ticks, 0.77% [5/648] of nymphs, 0.00% [0/555] of larvae). Babesia venatorum was detected in 0.42% (6/1,430) of ticks (0.44% [1/227] of adult ticks, 0.77% [5/648] of nymphs, 0.00% [0/555] of larvae) and B. capreoli in 0.07% (1/1,430) of ticks (0.00% [0/227] of adult ticks, 0.15% [1/648] of nymphs, 0.00% [0/555] of larvae). Despite the fact that no B. divergens-positive ticks were found, the collected data suggest a geographical spread of the pathogen on the farm. Bovine babesiosis remains a disease of veterinary importance in Europe and may cause considerable economic losses when (re-)emerging in non-endemic areas, especially as awareness for the disease among veterinarians and farmers declines.

Molecular detection of Babesia divergens and Mycoplasma wenyonii infection in cattle from Bosnia And Herzegovina

We report two cases of bovine babesiosis caused by Babesia divergens in a region of central Bosnia and Herzegovina. The cases were detected in June 2017 and July 2018 from two small backyard farms. Routine clinical assessments, including physical examination and haematology, revealed lethargy, fever, anaemia, leukopenia and haemoglobinuria in the affected animals. Serum alterations included an elevation of aspartate aminotransferase and a decrease of serum phosphate or hypophosphatemia. Thrombocytopenia was detected in the first clinical case. Microscopic examination of blood smears revealed intracytoplasmic protozoan parasites from the genus Babesia. Molecular screening of both animals confirmed the presence of Babesia divergens, the causative agent of bovine babesiosis. B. divergens DNA was also detected in two engorged female Ixodes ricinus ticks removed from these animals. In addition, Mycoplasma wenyonii DNA was identified by molecular screening in the animal examined in June 2017, and in I. ricinus ticks feeding on this animal. This study provides molecular confirmation of B. divergens as a cause of piroplasmosis in cattle in South-East Europe. The detection of M. wenyonii DNA ain I. ricinus also provides the first evidence of this bacterium in ticks in Europe.

Calculation of the required transfusion volume in anaemic Holstein calves

In bovine medicine, blood transfusion practice represents an emergency therapy where time is critical. The aim of this study was to develop a mathematical model to calculate the required blood for transfusion, using parameters which could be easily determined on the spot. Twenty Holstein calves were assigned to two groups depending on body weight (100.1 ± 3.1 kg and 151.1 ± 3.0 kg, respectively). All animals were subjected to an anaemia induction protocol in isovolaemic conditions in order to reduce the packed cell volume (PCV) by more than one third. Twenty-four hours later, each group received an auto-transfusion therapy. In order to find a valid constant for specific weight categories with high confidence interval in cattle, we calculated the value of constant 'CC' for each individual, using a formula described for carnivores as a basis. The value of the constant for the 100.1 ± 3.1 kg and 151.1 ± 3.0 kg groups was 80.6315 ± 1.1069 and 76.5294 ± 2.5640, respectively. The comparison between the two groups demonstrated significantly different mean values (P = 0.0002, by t-test) and, furthermore, significantly different values of the constant distributions (P = 0.0001, by the Kolmogorov-Smirnov test).

Diversity of Haemaphysalis-associated piroplasms of ruminants in Central-Eastern Europe, Hungary

Background

Increasing numbers of genetic variants are being recognized among piroplasms, but the precise taxonomical status, the tick vector and the geographical range of several species or genotypes are still unknown. Bovine piroplasmosis was reported to re-emerge in north-east Hungary. Because Theileria-infection was newly diagnosed in one cattle herd in the same region of the country, the aim of this study was to molecularly identify the relevant agent, to find its local vector tick species, and to examine the range of Babesia/Theileria spp. of ruminants in Haemaphysalis sp. ticks collected previously in Hungary.

Findings

Blood samples were drawn on two occasions from 90 dairy cattle in northern Hungary, and ticks were collected on their pastures. In addition, questing ticks (315 Haemaphysalis inermis, 259 H. concinna and 22 H. punctata), which originated mainly in the same region of the country from 2007, were included in the study. DNA was extracted from these samples, followed by molecular analysis for piroplasms.

In the cattle Theileria orientalis was identified, with 100 % sequence homology to isolates from Japan, China, South-Africa and Australia. Based on GenBank data this genotype has not been previously reported in Europe. The prevalence of infection in the herd remained almost constant in the main tick season, suggesting exposure in previous years.

Retrospective analysis of ticks revealed the presence of Babesia crassa in H. inermis, for the first time in Europe and in this tick species. On the other hand, H. concinna carried five different piroplasms, including B. motasi that was also newly detected in Central-Eastern Europe and in this tick species; whereas H. punctata harboured Theileria sp. OT3, hitherto known to occur in the Mediterranean region.

Conclusions

Results of this study broaden the range of piroplasms that are infective for ruminants in Central-Eastern Europe. Although bovine babesiosis and theileriosis was known to occur in Hungary, molecular evidence is provided here for the first time on the presence of Babesia and/or Theileria spp. of sheep, goats and cervids in Hungary.

Re-emergence of bovine piroplasmosis in Hungary: has the etiological role of Babesia divergens been taken over by B. major and Theileria buffeli?

BACKGROUND

The prevalence of bovine babesiosis caused by Babesia divergens has been declining during the past decades in northeastern Hungary, and no cases have been observed since 2008. Infections of cattle with B. major and Theileria buffeli were hitherto reported in southern and western Europe. In other parts of the globe, there is evidence of emergence and a growing clinical importance of T. buffeli and closely related genotypes of the T. orientalis complex.

FINDINGS

In a herd of 88 beef cattle kept in northeastern Hungary, bovine piroplasmosis was diagnosed in nine animals through the examination of blood smears or by molecular methods. B. major was identified in five animals, two of which died. In addition, four cattle harboured T. buffeli, and one of these animals was anaemic. Despite their presence, a contributory role of Anaplasma marginale and A. phagocytophilum could not be established in the disease cases.

CONCLUSIONS

In this study B. major and bovine theileriosis is reported for the first time in central-eastern Europe, where clinical cases were associated with a mild winter.

Changing incidence of bovine babesiosis in Ireland

BACKGROUND

In Ireland bovine babesiosis is caused by the tick-borne blood parasite, Babesia divergens. A survey of veterinary practitioners and farmers in the 1980's revealed an annual incidence of 1.7% associated with considerable economic losses. However, two subsequent surveys in the 1990's indicated a decline in clinical babesiosis. Recent evidence from continental Europe suggests that, probably due to climate change, the distribution of the tick vector of B. divergens, Ixodes ricinus is extending to more northerly regions and higher altitudes. In addition, milder winters are thought to widen the window of tick activity. In order to determine whether any such changes have affected the incidence of bovine babesiosis in Ireland, a questionnaire survey of farmers and veterinarians was carried out and compared with data from previous surveys.

RESULTS

Our survey indicates that while the incidence of clinical disease has continued to decline, cases can occur at any time of year. In contrast to previous surveys, affected farms were the same size as unaffected ones. There was no correlation between disease risk and the presence of deer on the land. Disease severity and mortality rates were increased because many infections were advanced by the time they were detected and treated.

CONCLUSION

While the precise reasons for the decline in the incidence of redwater are unknown, changes in agricultural practice are likely to be of importance. A reversal of the trend could be devastating, as vigilance among farmers and veterinarians is flagging and the national herd is losing its protective immunity to disease.