Anaplasma phagocytophilum seroprevalence in equids: a survey in Sicily (Italy)

Common and atypical presentations of Anaplasma phagocytophilum infection in equids with emphasis on neurologic and muscle disease

BACKGROUND

Comprehensive descriptions of equids with granulocytic anaplasmosis (EGA) with neurologic or muscle disease and other atypical presentations are scarce in the literature.

OBJECTIVE

Describe the clinical signs, laboratory findings, treatment, and outcome of equids with EGA with emphasis on neurologic and muscle disease.

ANIMALS

Thirty-eight horses, 1 donkey.

METHODS

Retrospective study. Equids with EGA were included. The electronic data base was searched from January 2000 to December 2022 using the words anaplasmosis, ehrlichiosis, granulocytic, and rickettsia. Signalment and clinical data were reviewed. Data were evaluated for normality using Shapiro-Wilk test. Parametric and nonparametric statistics were used for normally and non-normally distributed data.

RESULTS

Common (41%) and other (59%) presentations were seen in horses ≥ 4 years of age (median, 14 years) with an overrepresentation of males (77%). Neurologic disease was common (41%), mainly presenting as diffuse symmetrical proprioceptive ataxia. Brain disease was less common manifesting as obtundation and cranial nerve deficits. Muscle disease was less common, with QH breeds with the variant causing myosin heavy chain myopathy (MYHM) having severe disease. Cavitary effusion, cardiomyopathy and disseminated intravascular coagulation (DIC) were uncommon. Clinical laboratory results varied depending on disease stage. Muscle enzyme activities were significantly higher in horses with muscle disease. Outcome was favorable with prompt tetracycline treatment. Death and long-term sequelae were not reported.

CONCLUSIONS AND CLINICAL IMPORTANCE

Common and atypical presentations of EGA have a favorable outcome with prompt tetracycline treatment. Quarter horse breeds with muscle disease should be genotyped for MYHM.

Equine Granulocytic Anaplasmosis

Equine granulocytic anaplasmosis is a clinically significant and common disease of equids that has a broader prevalence than was once thought. The most common clinical signs include high fever and edema, with mild to mderate thrombocytopenia and lymphopenia typically noted on complete blood count. Subclinical cases are reported and many are self-limiting. Rare clinical presentations include neurologic disease, vasculitis, dysphagia, rhabdomyolysis, or bicavitary effusion. Most cases resolve rapidly with appropriate antimicrobial intervention.

Molecular detection and characterization of Anaplasma spp. in cattle and sable antelope from Lusaka and North-Western provinces of Zambia

Rickettsiales of the genus Anaplasma are globally distributed tick-borne pathogens of animals and humans with complex epidemiological cycles. Anaplasmosis is an important livestock disease in Zambia but its epidemiological information is inadequate. This study aimed to detect and characterize the species of Anaplasma present in domestic and wild ruminants in Zambia with a focus on the infection risk posed by the translocation of sable antelope (Hippotragus niger) from North-Western Province to Lusaka Province. Archived DNA samples (n = 100) extracted from whole blood (sable n = 47, cattle n = 53) were screened for Anaplasmataceae using 16S rRNA partial gene amplification followed by species confirmation using phylogenetic analysis. Out of the 100 samples, Anaplasma species were detected in 7% (4/57) of the cattle and 24% (10/43) of the sable antelope samples. Of the 14 positive samples, five were determined to be A. marginale (four from cattle and one from sable), seven were A. ovis (sable) and two were A. platys (sable). Phylogenetic analysis of the 16S rRNA partial gene sequences revealed genetic proximity between A. ovis and A. marginale, regardless of host. The detection of Anaplasma in wildlife in Zambia shows the risk of transmission of Anaplasma species associated with wildlife translocation.

Immune and Inflammatory Response of Donkeys (Equus asinus) Tested Positive to Tick-borne Pathogens

Among infection diseases transmitted by arthropods, the equine vector-borne diseases transmitted by ticks represent an emerging problem worldwide due to their morbidity and mortality and, in some cases, to their zoonotic relevance. Understanding the host immune/inflammatory response to the pathogens is crucial to develop effective methods of diagnosis, control and treatment. This study aimed to evaluate red blood cells (RBC), hematocrit (Hct), hemoglobin concentration (Hb), mean cell volume (MCV), mean cell hemoglobin content (MCH), mean cell hemoglobin (MCHC), platelets (PLT), white blood cells (WBC), leukocytes populations, and serum protein pattern of Sardinian donkeys scored positive to tick-borne pathogens. Thirty donkeys were dived in five groups, six subjects each: Group 1, tested negative to pathogens (control group); Group 2, donkeys infected by Theileria equi; Group 3, donkeys infected by Ehrlichia equi; Group 4, donkeys infected by Rickettsia Rickettsii; Group 5, donkeys co-infected by T. equi, E. equi and R. Rickettsii. From donkeys blood samples were collected and haematological and serum protein profiles were assessed. One-way ANOVA showed lower red blood cells, haemoglobin, platelets, lymphocytes and neutrophils values, and higher eosinophils, basophils, serum total proteins, α2-, β- and γ- globulins values in donkeys infected by one or more pathogens compared to control group (P < .05). The study highlighted an immune and inflammatory response of donkeys positive to E. equi, T. equi, and R. Rickettsii and represents a starting point for further investigations in the field to fill the gaps currently existing on the complex interwoven relationship between the pathogen and host immune and inflammatory response in equids.

Distribution of Tick-Borne Pathogens in Domestic Animals and Their Ticks in the Countries of the Mediterranean Basin between 2000 and 2021: A Systematic Review

Tick-borne pathogens (TBPs) include a wide range of bacteria, parasites and viruses that cause a large spectrum of animal, human and zoonotic tick-borne diseases (TBDs). The object of this review was to establish an inventory and an analysis of TBPs found in domestic animals in the countries of the Mediterranean Basin. This geographic area occupies a central position between several continents and is an area of movement for animals, humans and pathogens of interest and their vectors, which is important in terms of animal and human health. In this systematic review, we included a total of 271 publications produced between 2000–2021 concerning TBPs in domestic animals. Among this literature, we found a total of 90 pathogen species (known as TBPs) reported in the 20 countries of the area; these were detected in tick species from domestic animals and were also directly detected in domestic animals. In all, 31 tick species were recorded and 12 domestic animal species, the latter comprising nine livestock and three pet species. More than 50% of the publications were from Western Europe. Island data were extracted and assessed, as islands of the Mediterranean Basin were represented in 16% of the publications and 77.8% of the TBPs reported. Our results show the importance of islands in the monitoring of TBPs, despite the low percentage of publications.

Seroprevalence of Tick-Borne Infections in Horses from Northern Italy

Simple Summary

Equine vector-borne diseases, which include equine granulocytic anaplasmosis (EGA) and equine piroplasmosis (EP), are caused by several pathogens transmitted to horses by ticks. Considering the spread of equine vector-borne diseases in Italy and worldwide, a study was planned to investigate the seroprevalence of Anaplasma phagocytophilum and the other two selected pathogens, Theileria equi and Babesia caballi, in northern Italy. Data obtained from the present study demonstrated a high seroprevalence for all the three surveyed tick-borne pathogens and emphasized the importance of establishing control programs with the adoption of certain practices, including tick control, correct horses management, serological screening, regular usage of long-lasting acaricides and proper treatment of positive and clinically infected animals.

Abstract

Tick-borne diseases in horses are considered an emergent problem worldwide; the geographical redistribution of ticks, due to climatic and ecological changes, and the movements of infected horses between different nations play important roles in the spread of tick-borne diseases affecting these hosts. In this study, a survey was planned to estimate the seroprevalence of the Gram-negative bacterium Anaplasma phagocytophilum and the piroplasmid protozoa Babesia caballi and Theileria equi in Italian horses, as well as to evaluate possible risk factors associated with seropositive cases. Serum samples from 261 horses reared in northern Italy were collected and analyzed by indirect immunofluorescence antibody test for the detection of A. phagocytophilum-, B. caballi- and T. equi-specific antibodies. The overall seroprevalence to at least one of the investigated pathogens was 51%; sixty-one horses were seropositive to A. phagocytophilum (23.4%), forty-nine to B. caballi and the same number to T. equi (18.8% each). Seropositivity for more than one of the investigated agents was detected in thirty-two horses and the most common co-infection was observed between B. caballi and T. equi (5.7%). A significant risk factor for all the three pathogens was the elevation above sea level; indeed, the risk of infection was higher with an increase and decrease in elevation for A. phagocytophilum and for B. caballi and T. equi, respectively. Tick control in horses is strongly recommended considering the high seroprevalence values of transmitted pathogens.

Nonlinear Mixed-Effect Pharmacokinetic Modeling and Distribution of Doxycycline in Healthy Female Donkeys after Multiple Intragastric Dosing-Preliminary Investigation

Doxycycline (DXC) is a broad-spectrum antibacterial antimicrobial administered to horses for the treatment of bacterial infections which may also affect donkeys. Donkeys have a different metabolism than horses, leading to differences in the pharmacokinetics of drugs compared to horses. This study aimed to describe the population pharmacokinetics of DXC in donkeys. Five doses of DXC hyclate (10 mg/kg) were administered via a nasogastric tube, q12 h, to eight non-fasted, healthy, adult jennies. Serum, urine, synovial fluid and endometrium were collected for 72 h following the first administration. Doxycycline concentration was measured by competitive enzyme immunoassay. Serum concentrations versus time data were fitted simultaneously using the stochastic approximation expectation-maximization algorithm for nonlinear mixed effects. A one-compartment model with linear elimination and first-order absorption after intragastric administration, best described the available pharmacokinetic data. Final parameter estimates indicate that DXC has a high volume of distribution (108 L/kg) as well as high absorption (10.3 h^-1) in donkeys. However, results suggest that oral DXC at 10 mg/kg q12 h in donkeys would not result in a therapeutic concentration in serum, urine, synovial fluid or endometrium by comparison to the minimum inhibitory concentration of common equine pathogens. Further studies are recommended to identify appropriate dosage and dosing intervals of oral DXC in donkeys.

Serological Evidence of Natural Exposure to Tick-Borne Pathogens in Horses, Romania

The purpose of this study was to investigate the seroprevalence of selected tick-borne-pathogens (TBPs) among Romanian horses. For this, a total of 223 animals originating from north, central, and southeast Romania, including horses from stud farms (n = 118) and working horses (n = 105), were tested using a commercial rapid ELISA-based test. Overall, 10.3% (95% confidence interval (CI): 6.7-15.1%) of the tested horses were seropositive for antibodies (Ab) against Anaplasma phagocytophilum. Additionally, 18.8% (95% CI: 13.9-24.6%) and 0.5% (95% CI: 0.01-2.5%) of horses were seropositive for Ab against Borrelia burgdorferi sensu lato and Ehrlichia spp., respectively. Among the tested horses, 3.1% were seroreactive to two or three pathogens. These findings show the natural exposure of Romanian horses to zoonotic tick-borne pathogens and emphasize the need for further studies to better understand the epidemiology of equine tick-borne diseases in Romania.

Equine Granulocytic Anaplasmosis, A Neglected Disease: Risk Factors Associated with Prevalence of Antibodies in Equines

Background:

Anaplasma phagocytophilum, a tick-borne bacterium that causes granulocytic anaplasmosis, is a neglected pathogen in Brazil, and is diagnosed in several species of domestic and wild animals as well as in humans.

Objective:

This study aimed to investigate the prevalence of anti-A. phagocytophilum antibodies in Equidae from the state of Rio de Janeiro and to identify possible risk factors for infection.

Materials and Methods:

A total of 612 blood samples were collected from horses from 15 municipalities within the state. Moreover, an epidemiological questionnaire was administered to evaluate aspects related to seroreaction, taking into account the spatial distribution (properties, municipalities, and mesoregions), management practices, signs of disease, and the individual state of the animals. For the diagnosis, indirect immunofluorescence was performed.

Results:

In the present study, 124 (20.26%), out of a total of 612, animals with anti-A. phagocytophilum IgG antibodies at titers of 1:80 were detected. Multivariate logistic regression analysis showed that the presence of the infection at the property (P <0.0001) and the origin (P = 0.0095) of the horse were the true risk factors for infection in the state of Rio de Janeiro.

Conclusion:

This allows to infer that the bacterium is distributed in all mesoregions of the state of Rio de Janeiro and that animals from other states can introduce the infection and make a property a focus of disease; it can also be inferred that these properties are important in the maintenance of the disease and the permanence of bacteria circulating in horses. It is also noteworthy that this was the first identification of mules as hosts of A. phagocytophilum infection.

Serological Evidence of Anaplasma phagocytophilum and Spotted Fever Group Rickettsia spp. Exposure in Horses from Central Italy

Anaplasma phagocytophilum and Rickettsia spp. are tick-borne bacteria of veterinary and human concern. In view of the One-Health concept, the present study wanted to evaluate the spreading of these pathogens in horses living in central Italy. In particular, the aim of the investigation was to verify the exposure to A. phagocytophilum in order to update the prevalence of this pathogen in the equine population from this area, and to spotted fever group (SFG) Rickettsia spp. to evaluate a possible role of horses in the epidemiology of rickettsiosis. Indirect immunofluorescent assay was carried out to detect antibodies against A. phagocytophilum and SFG (spotted fever group) Rickettsia spp. in blood serum samples collected from 479 grazing horses living in central Italy during the period from 2013 to 2018. One hundred and nine (22.75%) horses were positive for A. phagocytophilum, 72 (15.03%) for SFG Rickettsia spp., and 19 (3.96%) for both antigens. The obtained results confirm the occurrence of A. phagocytophilum in equine populations, and also suggest the involvement of horses in the epidemiology of SFG rickettsiosis. In both cases, in view of the zoonotic aspect of these pathogens and the frequent contact between horses and humans, the monitoring of equine populations could be useful for indication about the spreading of the tick-borne pathogens in a certain geographic area.

Equine Granulocytic Anaplasmosis 28 years later

Equine granulocytic anaplasmosis (EGA) is an important tick borne disease of equines that is caused by Anaplasma phagocytophilum (A. phagocytophilum). The etiological agent has veterinary as well as public health importance because of its zoonotic nature. A. phagocytophilum causes an acute illness in equines with loss of appetite, lethargy, hemorrhages and lameness. Clinically, EGA is diagnosed upon examination of morulae within neutrophils especially granulocytes in the blood. The best diagnostic tool for the detection of EGA is Polymerase chain reaction (PCR). Previous studies suggested that EGA is a self-limiting disease and tetracycline therapy is considered as a best treatment regimen. There is no comprehensive summary on the occurrence and distribution of the infection at global level. Therefore, we intended to provide a comprehensive summary on the prevalence and epidemiology of EGA in different areas of the world. It includes mapping the global distribution of EGA in different areas of the world to identify the endemic regions which may be a source of potential disease outbreak. For this purpose, the published data from 1990 to 2018 on EGA was reviewed and collected by electronic literature search of five databases including Google, Google Scholar, Science Direct, PubMed and Web of Science.

First molecular evidence of equine granulocytic anaplasmosis in Pakistan

Anaplasma phagocytophilum (A. phagocytophilum) is an obligate intracellular bacterium that causes equine granulocytic anaplasmosis (EGA) disease in equines. This pathogen has zoonotic potential, which makes it very important to be detected and controlled as early as possible. This study was aimed to assess the molecular prevalence, associated risk factors of EGA along with its effects on various hematological parameters. This study revealed an overall 10.67% prevalence in equine. Horses showed highest prevalence followed by mules and donkeys presenting 11.86, 10.53 and 9.43% prevalence, respectively. The samples were confirmed for anaplasmosis through sequencing. The BLAST queries confirmed very high homology of our isolates with Chinese and Japanese isolates of A. phagocytophilum (Accession no's; KX505303, KY242456 and LC002836). The phylogenetic analysis found the study isolates clustered with each other and this cluster closely resembled Chinese isolate of A. bovis (FJ169957), A. phagocytophilum (HQ872464) and A. phagocytophilum (NR_044762) human isolate from northern Minnesota and Wisconsin. The key risk factors identified for occurrence of EGA in equine species on the basis of univariable analysis were sex of animal, housing type, tick infestation, previous tick history and tick control status, type of acaricides used, rearing system and farm hygiene, respectively. The hematological parameters like Hemoglobin (Hb), Total Leukocyte Count (TLC), Total Erythrocytes Count (TEC), and granulocytes were decreased in diseased animals. The mules showed no typical hematological variations which make sense for its nature as carrier of infection to the susceptible species. This is the first molecular evidence of EGA in Pakistan. The disease needs to be handled seriously as it has zoonotic potential. The animals should be properly attended in disease conditions as leukopenia, neutropenia and lymphopenia can aggravate the condition by making the animal prone to secondary infections.

Detection of Anaplasma phagocytophilum in red foxes (Vulpes vulpes) and raccoon dogs (Nyctereutes procyonoides) from Brandenburg, Germany

Anaplasma phagocytophilum is an obligate intracellular and tick-transmitted bacterium, which causes granulocytic anaplasmosis in animals and humans. Although infection with A. phagocytophilum in domestic animals and vector ticks is documented, there is sparse information on the occurrence of A. phagocytophilum in wild animals. Red foxes (Vulpes vulpes) as well as raccoon dogs (Nyctereutes procyonoides) are wildlife species highly abundant in certain areas of Germany and represent a potential wildlife reservoir for zoonotic diseases. To obtain data about the occurrence of A. phagocytophilum in these animals, red fox and raccoon dog carcasses (hunted or found dead) were collected from January to September 2009 in the Federal State of Brandenburg, Germany. Lung tissue samples were subjected to DNA extraction and were examined for the presence of A. phagocytophilum DNA by means of real-time PCR. Anaplasma phagocytophilum was detected in 10 out of 122 (8.2%) lungs of red foxes and in 3 out of 13 (23%) lungs of raccoon dogs. To the best of our knowledge, A. phagocytophilum was detected for the first time in red foxes and raccoon dogs in Germany.

Anaplasma phagocytophilum--a widespread multi-host pathogen with highly adaptive strategies

The bacterium Anaplasma phagocytophilum has for decades been known to cause the disease tick-borne fever (TBF) in domestic ruminants in Ixodes ricinus-infested areas in northern Europe. In recent years, the bacterium has been found associated with Ixodes-tick species more or less worldwide on the northern hemisphere. A. phagocytophilum has a broad host range and may cause severe disease in several mammalian species, including humans. However, the clinical symptoms vary from subclinical to fatal conditions, and considerable underreporting of clinical incidents is suspected in both human and veterinary medicine. Several variants of A. phagocytophilum have been genetically characterized. Identification and stratification into phylogenetic subfamilies has been based on cell culturing, experimental infections, PCR, and sequencing techniques. However, few genome sequences have been completed so far, thus observations on biological, ecological, and pathological differences between genotypes of the bacterium, have yet to be elucidated by molecular and experimental infection studies. The natural transmission cycles of various A. phagocytophilum variants, the involvement of their respective hosts and vectors involved, in particular the zoonotic potential, have to be unraveled. A. phagocytophilum is able to persist between seasons of tick activity in several mammalian species and movement of hosts and infected ticks on migrating animals or birds may spread the bacterium. In the present review, we focus on the ecology and epidemiology of A. phagocytophilum, especially the role of wildlife in contribution to the spread and sustainability of the infection in domestic livestock and humans.

Detection of Anaplasma marginale in Hyalomma asiaticum ticks by PCR assay

A polymerase chain reaction (PCR) assay was performed in this study to amplify the major surface protein 5 (msp5) gene from the genomic DNA of Anaplasma marginale in Hyalomma asiaticum ticks by species-specific primers. Sequence analysis showed that the msp5 gene was 643 bases long and that the PCR products from the samples had an identical sequence (JX507127). Moreover, the BLAST showed that the sequence was identical to the msp5 sequences of A. marginale and most closely related to the A. marginale msp5 gene (AB704328) and the Liangdang strain of the A. marginale msp5 gene (EF546443) with similarity of 99 % (differing only by two bases). An epidemiological survey was performed in several dairy farms: a total of 68 ticks were collected from 49 cattle. As a result, 14 of the 49 (28.57 %) blood smears stained with Wright-Giemsa and 22 of the 68 (32.35 %) ticks examined by PCR assay exhibited A. marginale infection. The results of the PCR assay were mostly consistent with the results of the microscopic examination. A number of results were negative in blood smear but positive in PCR, which is important for the early diagnosis of anaplasmosis.

Anaplasma phagocytophilum in horses and ticks in Tunisia

Background

Anaplasma phagocytophilum , the causative agent of granulocytic anaplasmosis, affects several species of wild and domesticated mammals, including horses. We used direct and indirect methods to compare and evaluate exposure to A. phagocytophilum in horses in northern Tunisia.

Methods

Serum from 60 horses was tested by IFA for antibodies to A. phagocytophilum , and whole blood was tested for A. phagocytophilum 16S rRNA gene using a nested-PCR. To examine the risk of A. phagocytophilum transmission, 154 ticks that had been collected from horses were examined for the presence of A. phagocytophilum by nested-PCR targeting 16S rRNA gene.

Results

This is the first time that A. phagocytophilum has been detected in horses in Tunisia, with an overall seroprevalence of 40/60 (67%). Six of the seroreactive samples (10%) had an IFA titer of 1:80, 14 (23%) of 1:160, 8 (13%) of 1:320 and 12 (20%) a titer 1 ≥ 640. The seroprevalence revealed no significant regional and sex differences. In contrast, a significant difference was observed between breeds. Eight (13%) of the horses were positive for A. phagocytophilum in the PCR, with no significant breed and age differences. Hyalomma marginatum was a predominant tick species (130/154), and 3 were infected by A. phagocytophilum (a prevalence of 2.3%). The concordance rate of A. phagocytophilum detection between IFA and PCR had a k value of −0.07.

Conclusions

The results presented in this study suggest that horses infested by ticks in Tunisia are exposed to A. phagocytophilum.