Prevalence and Risk Factors of Hypoglycemia in Virulent Canine Babesiosis

Hypoglycemia after Mitral Valve Repair in Dogs

Hypoglycemia has not been previously reported as a postoperative complication of mitral valve repair (MVR) in dogs; however, the authors have encountered cases of hypoglycemia after MVR. This study aimed to determine the incidence of hypoglycemia in dogs after MVR and investigate its causes. Blood glucose levels were measured at multiple timepoints in dogs undergoing MVR. Simultaneously, insulin and glucagon blood concentrations in dogs with hypoglycemia preoperatively and postoperatively were compared to verify the physiological responses to hypoglycemia. Furthermore, risk factors for hypoglycemia, using variables selected based on the characteristics of MVR and dogs undergoing MVR, were examined prospectively. The incidence of hypoglycemia after MVR was 14.2%, and plasma glucagon concentrations increased in these dogs (mean: 260 pg/mL and 644 pg/mL pre- and postoperatively, p < 0.001), whereas serum insulin concentrations decreased (median: 0.50 ng/mL and 0.29 ng/mL pre- and postoperatively, p = 0.002). Therefore, hyperinsulinemia or hypoglucagonemia is unlikely to be the cause of postoperative hypoglycemia. The identified risk factors for hypoglycemia included low body weight and asymptomatic myxomatous mitral valve disease. Monitoring blood glucose levels after MVR should be included in the standard hospitalization plan to prevent hypoglycemic emergencies in dogs.

The Diverse Pathogenicity of Various Babesia Parasite Species That Infect Dogs

Babesia species infect a very wide range of mammal hosts across the globe, and zoonotic infections are of growing concern. Several species of the Babesia genus infect dogs, and some of these cause significant morbidity and mortality. The Apicomplexan parasite resides within the red cell and infections result in direct damage to the host through intra- and extravascular hemolysis. An exuberant inflammatory response by the host to some species of Babesia parasites also results in significant collateral damage to the host. Canine infections have been the subject of many studies as the well-being of these companion animals is increasingly threatened by the spread of tick vectors and an increasingly mobile dog population. There are currently no widely available and effective vaccines, and effective treatment can be challenging. Understanding disease pathogenesis underlies the development of new treatments. The varying pathogenicity of the various Babesia parasite species that infect dogs offers an opportunity to explore the molecular basis for the wide range of diseases caused by infection with this parasite genus. In this review, we focus on what has been reported about the clinical presentation of Babesia-infected dogs in an attempt to compare the severity of disease caused by different Babesia species.

Molecular detection of Babesia spp. in dogs in Germany (2007-2020) and identification of potential risk factors for infection

BACKGROUND

In Europe, canine babesiosis is most frequently caused by Babesia canis and Babesia vogeli, and occasionally by Babesia gibsoni.. In Germany, B. canis is recognized as endemic. The aims of this study were to assess how often Babesia spp. infections were diagnosed in a commercial laboratory in samples from dogs from Germany, and to evaluate potential risk factors for infection.

METHODS

The database of the LABOKLIN laboratory was screened for Babesia spp.-positive polymerase chain reaction (PCR) tests for dogs for the period January 2007-December 2020. Sequencing was performed for positive tests from 2018 and 2019. Binary logistic regression analysis was performed to determine the effects of sex, season, and year of testing. Questionnaires were sent to the submitting veterinarians to obtain information on travel abroad, tick infestation, and ectoparasite prophylaxis of the respective dogs. Fisher's exact test was used to calculate statistical significance and P < 0.05 was considered statistically significant.

RESULTS

In total, 659 out of 20,914 dogs (3.2%) tested positive for Babesia spp. by PCR. Of 172 sequenced samples, B. canis was identified in 156, B. vogeli in nine, B. gibsoni in five, and B. vulpes in two. Season had a statistically significant impact on test results when summer/winter (1.6% tested positive) was compared to spring/autumn (4.7%), with peaks in April (5.2%) and October (7.4%) [P < 0.001, odds ratio (OR) = 3.16]. Sex (male 3.5%, female 2.8%; P = 0.012, OR = 1.49) and age (< 7 years old 4.0%, ≥ 7 years old 2.3%; P < 0.001, OR = 1.76) of the tested dogs also had a statistically significant effect. A statistically significant impact was demonstrated for observed tick attachment (P < 0.001, OR = 7.62) and lack of ectoparasite prophylaxis (P = 0.001, OR = 3.03). The frequency of positive Babesia spp. tests did not significantly differ between the 659 dogs that had never left Germany and the 1506 dogs with known stays abroad (P = 0.088).

CONCLUSIONS

The possibility of canine infection with B. canis needs to be especially taken into consideration in spring and autumn in Germany as the activity of the tick Dermacentor reticulatus, a potential vector for canine babesiosis, is highest in these seasons. Travel and importation of dogs are considered major factors associated with canine babesiosis in Germany. However, autochthonous Babesia spp. infections also occur in a considerable number of dogs in Germany.

Combined Untargeted and Targeted Metabolomics Approaches Reveal Urinary Changes of Amino Acids and Energy Metabolism in Canine Babesiosis With Different Levels of Kidney Function

Canine babesiosis is a tick-borne disease with a worldwide distribution, caused by the haemoprotozoan parasites of the genus Babesia. One of the most prevalent complication is acute kidney injury, and an early diagnosis of altered kidney function remains a challenge for veterinary practice. The aim of this study was to assess the urine metabolic profile from dogs with babesiosis and different degree of kidney function using untargeted and targeted MS-based metabolomics approaches. In this study, 22 dogs naturally infected with Babesia canis and 12 healthy dogs were included. Untargeted metabolomics approach identified 601 features with a differential abundance between the healthy group and groups of dogs with babesiosis and different level of kidney function, with 27 of them identified as a match to known standards; while targeted approach identified 17 metabolites with significantly different concentrations between the groups. A pattern of significantly altered metabolites referring to the inflammatory host response, oxidative stress, and energy metabolism modulation in babesiosis was presented. Our findings have demonstrated that kidney dysfunction accompanying canine babesiosis was associated with changes in amino acid metabolism, energy metabolism, fatty acid metabolism, and biochemical pathways such as urea cycle and ammonia detoxication. These findings will enable the inclusion of urinary markers for the detection and monitoring of renal damage in babesiosis, as well as in other similar diseases.

Experimental Babesia rossi infection induces hemolytic, metabolic, and viral response pathways in the canine host

Background

Babesia rossi is a leading cause of morbidity and mortality among the canine population of sub-Saharan Africa, but pathogenesis remains poorly understood. Previous studies of B. rossi infection were derived from clinical cases, in which neither the onset of infection nor the infectious inoculum was known. Here, we performed controlled B. rossi inoculations in canines and evaluated disease progression through clinical tests and whole blood transcriptomic profiling.

Results

Two subjects were administered a low inoculum (10⁴ parasites) while three received a high (10⁸ parasites). Subjects were monitored for 8 consecutive days; anti-parasite treatment with diminazene aceturate was administered on day 4. Blood was drawn prior to inoculation as well as every experimental day for assessment of clinical parameters and transcriptomic profiles. The model recapitulated natural disease manifestations including anemia, acidosis, inflammation and behavioral changes. Rate of disease onset and clinical severity were proportional to the inoculum. To analyze the temporal dynamics of the transcriptomic host response, we sequenced mRNA extracted from whole blood drawn on days 0, 1, 3, 4, 6, and 8. Differential gene expression, hierarchical clustering, and pathway enrichment analyses identified genes and pathways involved in response to hemolysis, metabolic changes, and several arms of the immune response including innate immunity, adaptive immunity, and response to viral infection.

Conclusions

This work comprehensively characterizes the clinical and transcriptomic progression of B. rossi infection in canines, thus establishing a large mammalian model of severe hemoprotozoal disease to facilitate the study of host-parasite biology and in which to test novel anti-disease therapeutics. The knowledge gained from the study of B. rossi in canines will not only improve our understanding of this emerging infectious disease threat in domestic dogs, but also provide insight into the pathobiology of human diseases caused by Babesia and Plasmodium species.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07889-4.

Molecular evidence indicts Haemaphysalis leachi (Acari: Ixodidae) as the vector of Babesia rossi in dogs in Nigeria, West Africa

Babesia rossi is the most pathogenic among the large canine babesias and it is the major cause of canine babesisosis in Nigeria. In South Africa it is transmitted by Haemaphysalis elliptica however, its putative vector in Nigeria where Rhipicephalus sanguineus is the most prevalent tick on dogs compared to Haemaphysalis species has not been ascertained. The incongruity between tick distribution and the frequent detection of B. rossi in Nigeria motivated this investigation to identify the local vector(s) of B. rossi. A total of 3805 ticks were collected from 363 naturally infested dogs from different parts of Nigeria. Of these numbers, 758 engorged female ticks; Rh. sanguineus (n = 660) and H. leachi (n = 98) were incubated for oviposition and hatching. After the completion of egg laying, Rh. sanguineus (n = 69) and H. leachi (n = 24) and their resulting progenies were screened for the presence of B. rossi DNA using a nested PCR targeting the 693 bp of the 18S rRNA gene of Babesia spp. Amplification and sequencing of B. rossi DNA was successful in the adults of H. leachi and their resulting egg and larval progenies but not in the adult Rh. sanguineus and progenies. The B. rossi DNA sequences from the H. leachi and their progenies have 99-100 % identity to each other and 98-99 % identical to sequences of B. rossi in GenBank (GenBank: MH143395.1), thus confirming transovarian passage. This evidence confirms for the first time following the reclassification of H. leachi to H. elliptica in South Africa the role of H. leachi in the transmission of B. rossi in dogs in Nigeria.

Prognostic markers and their discriminant score in predicting the outcome of Babesia gibsoni infection

BACKGROUND

We aimed to identify prognostic markers and their discriminant score in predicting the lethal outcome of canine Babesia gibsoni.

METHODS

Blood samples were collected from 108 client-owned dogs with clinical signs commensurate with babesiosis to analyze haematological, biochemical, haemostatic, antioxidant profile and thiobarbituric acid reactive substance levels. Samples were screened for Babesia infection (microscopic and molecular techniques). Babesiosis-affected dogs were classified into survivors and non-survivors, and 30 healthy dogs were used in the control group.

RESULTS

Haemoglobin, thrombocytes, catalase, urea, creatinine, alanine aminotransferase (ALT), alkaline phosphatase, lactate and reticulocytes were highly correlated to survival. Receiver operating characteristics analysis revealed urea, ALT and lactate as specific prognostic markers for the disease. The formula for calculation of discriminant scores (Di) for lethal outcome of the disease was generated with cut-off score 0.141. The scoring system was 79% sensitive and 83% specific in predicting the lethal outcome of the disease.

CONCLUSIONS

A scoring system developed from the prognosticating markers may aid in predicting the outcome of Babesia gibsoni infection on the day of presentation itself enabling intensive care for those animals with a cut-off score more than 0.141.

Elevated serum manganese concentration in dogs as a possible predisposing factor of cerebral babesiosis in dogs

The aim of this study was to demonstrate a relationship between the occurrence of clinical signs of brain involvement in dogs with babesiosis and the concentration of manganese (Mn) in their serum. The study included seven dogs with early babesiosis (Group 1), seven dogs with cerebral babesiosis (Group 2) and seven healthy dogs (Group 3). Haematological and biochemical blood tests were performed in all dogs, and the results were analysed statistically. The Mann-Whitney rank test was used to demonstrate the differences in Mn concentrations, as well as other haematological and biochemical parameters between groups. In dogs in Group 2 with cerebral babesiosis, as compared to dogs in Groups 1 and 3, a statistically significant increase in serum Mn concentration was shown (P = 0.002 and P = 0.029) that may have been associated with the development of anaemia and/or impairment of liver function. Given the well-established neurotoxic effects of Mn in humans, experimental rodents and primates, additional studies on the role of Mn in the pathogenesis of the cerebral form of canine babesiosis are warranted.

Prevalence of canine babesiosis and their risk factors among asymptomatic dogs in the federal capital territory, Abuja, Nigeria

Babesia sp. are intracellular parasitic organisms that affects mainly the red blood cells of most mammals, causing the disease known as babesiosis, and transmitted by ticks. Babesisosis is potentially fatal and a major disease of dogs in Nigeria. Therefore, active and routine surveillance is recommended. In this study, the infection was investigated among apparently healthy domestic dogs in six Area Councils of the Federal Capital Territory (FCT), Abuja, Nigeria with the aim of determining the prevalence of the infection and the associated risk factors. Blood samples were collected from dogs (n = 480) at randomly selected households, from September 2015 to August 2016. Data regarding sampling location, sex, age, breed, use, presence or absence of ticks were recorded. Blood smears were prepared, stained with Geimsa stain, and examined under light microscope for Babesia sp. The results showed an overall prevalence of 10.8% Babesia canis infection. The prevalence among dogs examined in the six Area Councils were 6.3%, 12.5%, 10.0%, 12.5%, 11.3%, and 12.5 % for Abaji, AMAC, Bwari, Gwagwalada, Kuje and Kwali Area Council, respectively. The prevalence was highest (12.5%) among dogs from Kwali, AMAC and Gwagwalada, and lowest 5 (6.3%) among dogs from Abaji. Of the infected dogs, 13.7% were females and 8.3%, males. Dogs between 12 < 36 months old had the highest (17.0%) prevalence of infection while those of >60 months of age had the lowest (4.5%). Based on breed, the infection was more prevalent among exotic dogs (12.9%) than cross breeds (9.4%). While none of pet dogs were positive for Babesia canis, prevalence of 11.1% and 11.3% were recorded for guard and hunting dogs, respectively. Tick infestation was recorded for 254 dogs of which 17.3% had Babesia canis while only 3.5% of 226 non-infested dogs were Babesia positive. Babesia infection during the rainy season was 14.6% while 3.5% of dogs were positive during dry season. The data on monthly prevalence showed that August and September had the highest (13.5%) prevalence while January and February had the lowest (2.0%). We conclude that the canine babesiosis in the FCT was significantly dependent on age, use of dogs, tick infestation, and season. Therefore, priorities should be given to these factors while instituting control measures against the infection.

Evaluation of acute kidney injury in dogs with complicated or uncomplicated Babesia rossi infection

Dogs with babesiosis can present with multiple complications, including acute kidney injury (AKI). The objective of this study was to characterize AKI in dogs with babesiosis caused by Babesia rossi at presentation and after treatment. Thirty-five client-owned dogs with B. rossi infection and 10 control dogs were included in this prospective observational study. Blood and urine were collected in Babesia-infected dogs at presentation (T₀, n = 35), after 24 h (T_24h, n = 11), and after 1 month (T_1m, n = 9). The following urinary kidney injury biomarkers were assessed: urinary protein to creatinine ratio (UPC), urinary glomerular injury biomarkers (immunoglobulin G (uIgG) and C-reactive protein (uCRP)), and urinary tubular injury biomarkers (retinol-binding protein (uRBP) and neutrophil gelatinase-associated lipocalin (uNGAL)). Serum functional renal biomarkers were creatinine (sCr) and symmetric dimethylarginine (sSDMA). Post-mortem kidney biopsies were analyzed by light and transmission electron microscopy. At T₀, all kidney injury biomarkers were significantly higher in Babesia-infected dogs compared to healthy controls (P < 0.001), while functional renal biomarkers were not significantly different (P > 0.05). At T_24h, all urinary tubular injury biomarkers and UPC decreased significantly (P < 0.01), while glomerular injury biomarkers did not (P = 0.084). At T_1m, all urinary kidney injury biomarkers decreased to values not significantly different from healthy controls (P > 0.5). Significant changes in functional renal biomarkers were not seen after treatment (P > 0.05). Dogs with complicated babesiosis had significantly higher glomerular injury biomarkers, UPC, and sSDMA compared to uncomplicated cases (P < 0.05), while all tubular injury biomarkers and sCr were not significantly different (P > 0.1). Dogs with babesiosis caused by B. rossi showed transient kidney injury, which was detected by all kidney injury biomarkers, but remained undetected by functional biomarkers. All infected dogs, irrespective of disease severity, suffered comparable kidney injury based on tubular injury biomarker concentrations, while loss of function was seen more often in dogs with complicated babesiosis based on sSDMA results.

A clinical and pathological description of 320 cases of naturally acquired Babesia rossi infection in dogs

Babesia rossi causes the most severe clinical disease in dogs of all the babesia parasites. We included 320 naturally-infected dogs that presented for care at the Onderstepoort Veterinary Academic Hospital between 2006 and 2016. All dogs had mono-infections confirmed by multiplex PCR. The data allowed more accurate clinical classification of the disease and identified parameters that were associated with disease severity and death. Odds ratios for dying were significant (P < 0.05) for increased band neutrophil count, collapse at presentation; presence of cerebral signs; hypoglycaemia; hyperlactatemia; high urea, high creatinine; hyperbilirubinaemia; hypercortisolaemia; and hypothyroxinaemia. Joint component analysis confirmed that the variables with significant odds ratios grouped together with death. Yet, multivariate logistic regression was unable to identify a group of significant independent predictors of death. Receiver Operator Characteristic curves indicated that low total thyroid hormone, high bilirubin, high serum urea and high cortisol concentrations were the variables with the highest sensitivity and specificity for death. These data provide both the clinician and researcher with a set of easily-measured laboratory and clinical assessments to classify cases into those that are uncomplicated and those that are complicated. The disease is complex and multisystemic and probably involves mechanisms more proximal in the pathogenesis than those that have been evaluated.

Vitamin D status in dogs with babesiosis

Canine babesiosis is a virulent infection of dogs in South Africa caused principally by Babesia rossi. Hypovitaminosis D has been reported in a wide range of infectious diseases in humans and dogs, and low vitamin D status has been associated with poor clinical outcomes. However, the relationship between vitamin D status and canine babesiosis has not been investigated. The objective of this study was to examine the relationship between the presence and severity of B. rossi infection and vitamin D status of infected dogs. Owners with dogs with a confirmed diagnosis of B. rossi infection and of healthy control dogs were invited to enrol onto the study. Vitamin D status was assessed by measurement of serum concentrations of the major circulating vitamin D metabolite, 25-hydroxyvitamin D (25[OH]D). Dogs with babesiosis (n = 34) had significantly lower mean serum 25(OH)D concentrations than healthy dogs (n = 24) (37.76 ± 21.25 vs. 74.2 ± 20.28 nmol/L). The effect of babesiosis on serum 25(OH)D concentrations was still significant after adjusting for any effect of age, body weight and sex. There was a negative relationship between serum 25(OH)D concentrations and disease severity in dogs with babesiosis. Serum concentrations of creatinine and alanine aminotransferase and time to last meal were not associated with serum 25(OH)D concentrations in dogs with babesiosis. In conclusion, dogs with Babesia rossi infections had lower serum 25(OH)D concentrations than healthy dogs. The inverse correlation between 25(OH)D concentrations and the clinical severity score indicate that hypovitaminosis D might be a helpful additional indicator of disease severity.

An annotated checklist of tick-borne pathogens of dogs in Nigeria

Tick-borne pathogens are transmitted by the bite of a tick vector or the ingestion therein by a susceptible host. Conventionally, the diagnosis of tick-borne parasites in Nigeria is achieved through the demonstration of their developmental stages in the host's blood or tissues. These classical methods are limited in their capability to detect chronic cases or healthy carriers and to differentiate between pathogens of similar morphological features. Molecular diagnostic techniques of high sensitivity have been developed to overcome these shortfalls by detecting the pathogen's DNA, elucidating their genetic makeup and comparing their phylogenetic relationship to other pathogens, sometimes necessitating taxonomic changes. Detection of DNA of canine tick-borne pathogens (CTBPs) such as Ehrlichia canis, Hepatozoon canis, and Mycoplasma haemocanis has been reported in Nigerian dogs corroborating earlier microscopic findings. Furthermore, DNA of Anaplasma platys, Ehrlichia ewingii, 'Candidatus Mycoplasma haemobos' and Theileria sp. hitherto considered to be absent in Nigeria has been detected, thereby expanding the spectrum of CTBPs in the country. However, in some cases, diagnoses based on the detection of single short DNA fragments from pathogens can cause considerable confusion. This occurred in the case of the large canine Babesia, previously referred to as Babesia canis which has been reported in Nigerian dogs. There appears to be confusion regarding the accurate status of this pathogen in Nigeria due to the subsequent classification into Babesia canis, Babesia vogeli and Babesia rossi. Moreover, several molecular studies failed to detect the DNA of Babesia gibsoni previously reported in Nigerian dogs by light microscope. These findings necessitate regular update of the list of CTBPs of veterinary and medical importance, in order to keep practitioners abreast with these changes. Herein, an annotated checklist of tick-borne pathogens of dogs in Nigeria, based on available data from both classical and molecular studies, with notes explaining any discrepancies between the methods and probable explanations thereof, is presented.

Pathophysiology and aetiology of hypoglycaemic crises

Hypoglycaemia is a common, life-threatening complication that occurs as a component of a wide variety of disease processes. Despite its frequent occurrence, information concerning the aetiology, characteristics and outcomes of hypoglycaemic crises in veterinary medicine is limited. This review summarises the current understanding of the pathophysiology of hypoglycaemia, the body's counter-regulatory response, underlying aetiologies, diagnosis and treatment. Disease mechanisms are discussed and published evidence in veterinary literature regarding prognostic indicators, prevalence, diagnosis and treatment is examined for hypoglycaemia-related disease processes including insulinoma, glucose-lowering toxins and medications.

Canine Babesiosis: Where Do We Stand?

Canine babesiosis is a tick-borne disease caused by protozoal haemoparasites of different Babesia species. Babesiosis is one of the most important globally extended and quickly spreading tick-borne infections of dogs. This comprehensive review gives an in-depth overview of Babesia species currently identified in dogs together with relevant vector tick species and their geographical distribution, life cycle and transmission of parasite. The main mechanisms in the pathogenesis of babesiosis are described and elucidated by recent literature overview. As Babesia infection causes a disease with very variable clinical manifestations, special attention is given to clinical signs, laboratory features and clinicopathological findings. The diagnosis of canine babesiosis by microscopy, serological and molecular methods is reviewed, together with recent advances in mass spectrometry based assays. Accurate detection and species recognition are important for the selection of the appropriate therapy, monitoring and prediction of the outcome of the disease. Finally, guidelines for the treatment and prevention of canine babesiosis are given.

MCP-1, KC-like and IL-8 as critical mediators of pathogenesis caused by Babesia canis

Canine babesiosis caused by the intraerythrocytic protozoan parasite Babesia canis is a tick-borne disease characterized by a host response that involves both cellular and humoral immunity. This study focuses on the secretion of cytokines Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF), Keratinocyte Chemotactic-like (KC-like), Interleukins (IL)-2, IL-7, IL-8, IL-10, IL-15, IL-18 and Monocyte Chemotactic Protein-1 (MCP-1) in babesiosis caused by Babesia canis upon treatment with Imizol®. We assessed time dependent changes in cytokine levels and tested whether these changes correlate with pathogenesis of the disease. Sixteen healthy dogs and 31 dogs infected with Babesia canis, of which 18 showed complications, were treated with Imizol®. One dog died during the study (3.2%). Longitudinal study was perfomed by monitoring dogs at the first day of presentation (day 1) and 6 days later (day 7). Our results show that higher MCP-1 levels on day 1 are positively associated with the occurrence of complications, (complicated vs. uncomplicated; p = 0.00016). A similar pattern was observed for KC-like on day 1 (p = 0.0326) and day 7 (p = 0.044). Moreover, babesiosis caused by B. canis produced a steady increase in IL-8 levels with a moderate to strong negative correlation with erythrocyte counts and hematocrit in uncomplicated diseased dogs only (Spearman's rank correlation coefficient rs = -0.582 and rs = -0.598 respectively). Like for MCP-1, KC-like levels also differed in complicated and uncomplicated diseased dogs on day 1 (p = 0.03236) and day 7 (p = 0.044). Furthermore, KC-like levels were strongly correlated with IL-8 levels (rs = 0.663-0.7) and non-segmented neutrophil counts (rs = 0.572-0.732) in both diseased groups. Analysis of ROC suggests the use of serum levels of MCP-1 and IL-7 as predictors of the occurrence of complications with an AUC of 0.906 and 0.896 respectively and linear combinations of MCP-1, KC-Like, IL-7 and GM-CSF with values up to AUC = 0.983. Cytokine cluster analysis presented in this study can contribute to a better understanding of the pathogenesis of babesiosis and serve as a prognostic tool for the early detection of cases with highest likelihood of developing complications. Overall, our studies show that infection by B. canis elicits a cytokine pattern that is distinct from that observed with B. rossi, and that some of the inflammatory mediators can be useful to predict complications. Our results also suggest targets for the development of novel therapeutic strategies in babesiosis caused by B. canis.

A flow cytometric assessment of the lymphocyte immunophenotypes in dogs naturally infected with Babesia rossi

Immunity to Babesia infection requires both innate and acquired responses, including cell mediated- and humoral responses. The aims of this study were to investigate the variation in selected peripheral blood lymphocyte phenotypes in dogs with virulent babesiosis at presentation and over time after treatment, and to determine whether these were correlated with the severity of clinical signs. Forty-four dogs naturally infected with B. rossi were studied and 5 healthy dogs were included as controls. Blood samples were collected from the jugular vein at admission, prior to any treatment, and at 24h and 48-72h. Leukocytes were incubated with canine specific, fluorochrome conjugated anti-CD3, anti-CD4, anti-CD8, and anti-B cell markers. Babesia-infected dogs were divided into complicated or uncomplicated groups on clinical grounds and in-house laboratory assays. The percentage CD3⁺ lymphocytes in the complicated group was lower compared to the controls (P=0.014) and uncomplicated group (P=0.007). The percentage CD4⁺ T lymphocytes in the complicated group was lower compared to the controls (P=0.027) and uncomplicated group (P=0.014). Both the complicated as well as the uncomplicated groups expressed a lower percentage CD8⁺ T lymphocytes compared to the control group (P<0.001 and P=0.005, respectively). The percentage B lymphocytes was higher in the complicated group at 48-72h. These findings could indicate the presence of a functional immune suppression secondary to increased apoptosis or redistribution of effector lymphocytes and/or a combination of other immune modulatory mechanisms induced by B. rossi infection.

A review of canine babesiosis: the European perspective

Canine babesiosis is a significant tick-borne disease caused by various species of the protozoan genus Babesia. Although it occurs worldwide, data relating to European infections have now been collected for many years. These data have boosted the publication record and increased our working knowledge of these protozoan parasites. Both the large and small forms of Babesia species (B. canis, B. vogeli, B. gibsoni, and B. microti-like isolates also referred to as "B. vulpes" and "Theileria annae") infect dogs in Europe, and their geographical distribution, transmission, clinical signs, treatment, and prognosis vary widely for each species. The goal of this review is to provide veterinary practitioners with practical guidelines for the diagnosis, treatment and prevention of babesiosis in European dogs. Our hope is that these guidelines will answer the most frequently asked questions posed by veterinary practitioners.

Prognostic Markers in Acute Babesia canis Infections

Background

Canine babesiosis, caused by Babesia canis, is a prevalent and clinically relevant disease in Europe. Severe acute babesiosis is characterized by a high mortality but prognosis is not always correlated with clinical signs nor with the level of parasitemia.

Objective

This study evaluated prognostic markers associated with poor outcomes in acute Babesia canis infections.

Animals and Methods

We compared the results of routine laboratory profiles, hand‐held lactate and glucose analyzer, and the acute phase response in 2 groups of naturally infected dogs (7 survivors and 8 nonsurvivors). Samples were collected at the time of first admission and before any treatment. Subsequently, the course of prognostic markers was followed in 3 dogs experimentally inoculated with B. canis.

Results

Nonsurvivors showed significantly higher concentrations of lactate, triglycerides and phosphate and lower hematocrit, leukocyte counts, total serum protein concentrations, and thrombocyte counts when compared to survivors. All nonsurvivors (8/8) had hyperlactatemia, whereas most survivors (6/7) had values within the reference range. All survivors had leucocyte counts within the reference range, unlike the nonsurvivors, which showed leukopenia. During the course of acute babesiosis, the variables serum lactate, triglyceride, and phosphate concentrations, and thrombocyte count only exceeded a prognostic threshold during acute crisis.

Conclusions and clinical importance

Poor outcome in acute B. canis infection is indicated by changes in the laboratory profile. Intensive care should be considered for dogs presenting with moderate anemia, severe thrombocytopenia, mild to moderate leukopenia, hyperlactatemia, moderately increased serum phosphate, and triglyceride concentrations, and moderately decreased total serum protein concentrations.

Serum canine pancreatic-specific lipase concentrations in dogs with naturally occurring Babesia rossi infection

Babesia rossi is the cause of a highly virulent multisystemic disease with a variable outcome, which is a reliable model of systemic inflammatory response syndrome (SIRS). The objective of this study was to determine the concentration of canine pancreatic-specific lipase (cPL) in a population of dogs with naturally acquired B. rossi infection. In addition, the associations between serum cPL and death and SIRS status were examined. An observational study recruited 87 dogs diagnosed with B. rossi infection and serum cPL concentrations were measured daily until discharge or death. The median concentration of serum cPL was 124.0 µg/L (interquartile range: 51.0 µg/L - 475.5 µg/L) on admission (n = 87) and 145.5 µg/L (62.3 µg/L - 434.0 µg/L) on day two of hospitalisation (n = 40). Twenty-four dogs (28%) had a serum cPL concentration within the diagnostic range for pancreatitis (> 400 µg/L) at admission with 13 dogs (32.5%) presenting as such on the second day of hospitalisation. The median concentration of serum cPL in dogs with SIRS was 158 µg/L (interquartile range: 52.5 µg/L - 571.5 µg/L; n = 53), which was significantly higher than in those without SIRS (75 µg/L; 50.3 µg/L - 131.8 µg/L; n = 32) (P = 0.018). This study demonstrated that an unexpectedly high number of dogs diagnosed with naturally acquired canine babesiosis had a serum cPL concentration within the diagnostic range for acute pancreatitis and a significantly higher serum cPL concentration was found in dogs that were classified as having SIRS.

Clinical and laboratory findings of Babesia infection in dogs

Canine babesiosis is a worldwide tick borne disease. Dogs with fever, in appetence and enlarged lymph nodes were screened for the presence of haemoprotozoan parasites during the one year period of study at T.V.C.C., C.V.Sc., Proddatur. Based on the stained peripheral blood smears examination, six dogs were found to be affected with babesiosis. Clinical examination of the dogs revealed ticks over the body, congested conjunctival mucus membranes, dullness, fever, tachycardia, tachypnoea in all the dogs. Some of the dogs had icterus, lymphadenopathy, haemoglobinuria. Laboratory examination of the clinical samples revealed reduction in haemoglobin concentration, erythrocyte count, platelet count, serum total protein, serum albumin and glucose levels. Increased serum SGPT, creatinine, BUN levels were recorded. Dogs were treated with inj. Diminazene aceturate (Berenil RTU) @ 5 mg/kg body weight, single dose along with supportive and symptomatic therapy in individual cases.

Babesia: a world emerging

Babesia are tick-transmitted hemoprotozooans that infect mammals and birds, and which are acknowledged for their major impact on farm and pet animal health and associated economic costs worldwide. Additionally, Babesia infections of wildlife can be fatal if associated with stressful management practices; and human babesiosis, also transmitted by blood transfusion, is an increasing public-health concern. Due to the huge diversity of species reported to serve as Babesia hosts, all vertebrates might be potential carriers, as long as they are adequate hosts for Babesia-vector ticks. We here provide a comprehensive overview of the most relevant Babesia species, and a discussion of the classical taxonomic criteria. Babesia, Cytauxzoon and Theileria parasites are closely related and collectively referred to as piroplasmids. A possible scenario for the history of piroplasmids is presented in the context of recent findings, and its implications for future research avenues are outlined. Phylogenetic trees of all available 18S rRNA and hsp70 genes were generated, based on which we present a thoroughly revised molecular classification, comprising five monophyletic Babesia lineages, one Cytauxzoon clade, and one Theileria clade. Updated 18S rRNA and beta-tubulin gene trees of the B. microti isolates agree with those previously reported. To reconcile estimates of the origin of piroplasmids and ticks (~300 Ma, respectively), and mammalian radiation (60 Ma), we hypothesize that the dixenous piroplasmid life cycle evolved with the origin of ticks. Thus, the observed time gap between tick origin and mammalian radiation indicates the existence of hitherto unknown piroplasmid lineages and/or species in extant vertebrate taxa, including reptiles and possibly amphibians. The development and current status of the molecular taxonomy of Babesia, with emphasis on human-infecting species, is discussed. Finally, recent results from population genetic studies of Babesia parasites, and their implications for the development of pathogenicity, drug resistance and vaccines, are summarized.

Breed and sex risk factors for canine babesiosis in South Africa

BACKGROUND

In South Africa, canine babesiosis typically is an acute disease in susceptible individuals and is a major cause of morbidity and mortality. Despite the importance of the disease, there have been no large studies that have examined the influence of breed and sex on disease susceptibility.

HYPOTHESIS

Toy breeds have a lower risk of babesiosis than working dogs.

ANIMALS

A total of 1,222 dogs diagnosed with canine babesiosis and 11,484 noninfected dogs presented to the Onderstepoort Veterinary Academic Hospital's small animal outpatient clinic between 2004 and 2010.

METHODS

Retrospective study.

RESULTS

Intact male, neutered male, and neutered female dogs had a significantly higher odds of being diagnosed with canine babesiosis compared to intact female dogs. Five of the 6 Toy breeds had significantly lower odds of being diagnosed with canine babesiosis than did the reference breed, Labrador Retrievers. In contrast, none of the 8 working dog breeds had significantly lower odds compared to the reference breed.

CONCLUSIONS AND CLINICAL IMPORTANCE

Intact male, neutered male, and neutered female dogs were at increased risk of canine babesiosis compared to intact female dogs. Several dog breeds, notably Toy breeds, had a lower risk of babesiosis in a hospital population of dogs in South Africa. The mechanism or mechanisms by which Toy breeds are protected from developing canine babesiosis may be related to genetic background or environmental exposure and deserves further study.

Babesiosis in dogs and cats--expanding parasitological and clinical spectra

Canine babesiosis caused by different Babesia species is a protozoal tick-borne disease with worldwide distribution and global significance. Historically, Babesia infection in dogs was identified based on the morphologic appearance of the parasite in the erythrocyte. All large forms of Babesia were designated Babesia canis, whereas all small forms of Babesia were considered to be Babesia gibsoni. However, the development of molecular methods has demonstrated that other Babesia species such as Babesia conradae, Babesia microti like piroplasm, Theileria spp. and a yet unnamed large form Babesia spp. infect dogs and cause distinct diseases. Babesia rossi, B. canis and Babesia vogeli previously considered as subspecies are identical morphologically but differ in the severity of clinical manifestations which they induce, their tick vectors, genetic characteristics, and geographic distributions, and are therefore currently considered separate species. The geographic distribution of the causative agent and thus the occurrence of babesiosis are largely dependent on the habitat of relevant tick vector species, with the exception of B. gibsoni where evidence for dog to dog transmission indicates that infection can be transmitted among fighting dog breeds independently of the limitations of vector tick infestation. Knowledge of the prevalence and clinicopathological aspects of Babesia species infecting dogs around the world is of epidemiologic and medical interest. Babesiosis in domestic cats is less common and has mostly been reported from South Africa where infection is mainly due to Babesia felis, a small Babesia that causes anemia and icterus. In addition, Babesia cati was reported from India and sporadic cases of B. canis infection in domestic cats have been reported in Europe, B. canis presentii in Israel and B. vogeli in Thailand. Babesiosis caused by large Babesia spp. is commonly treated with imidocarb dipropionate with good clinical response while small Babesia spp. are more resistant to anti-babesial therapy. Clinical and parasitological cure are often not achieved in the treatment of small Babesia species infections and clinical relapses are frequent. The spectrum of Babesia pathogens that infect dogs and cats is gradually being elucidated with the aid of molecular techniques and meticulous clinical investigation. Accurate detection and species recognition are important for the selection of the correct therapy and prediction of the course of disease.

Why is Southern African canine babesiosis so virulent? An evolutionary perspective

Canine babesiosis is a common, highly virulent disease in Southern Africa with even pups and juveniles being severely affected. This contrasts with bovine babesiosis, for example, where host, parasite and vector co-evolved and young animals develop immunity after infection without showing clinical signs. Babesia rossi, the main causative organism of canine babesiosis in sub-Saharan Africa, was first described from a side-striped jackal (Canis adustus) in Kenya. Although data are meagre, there is evidence that indigenous African canids, such as jackals and wild dogs (Lycaon pictus), can harbour the parasite without showing untoward effects. Dogs are not indigenous to Africa. The vast majority of dogs presented at veterinary facilities in South Africa represent recently introduced European, Asian or American breeds. The contention is that B. rossi is a new challenge to which these dogs have not adapted. With intensive treatment of clinical cases, natural selection is effectively negated and the status quo will probably be maintained indefinitely. It is postulated that Babesia vogeli, which frequently results in unapparent infections or mild manifestations in dogs, represents or is closely related to the ancestral form of the canine parasite, possibly originating from wolves (Canis lupus).

Clinical management of canine babesiosis

OBJECTIVE

To review and summarize current information regarding epidemiology, pathogenesis, and pathophysiology leading to the various clinical syndromes associated with canine babesiosis. Diagnosis, treatment, preventative strategies, and zoonotic implications are discussed.

ETIOLOGY

Babesiosis is caused by hemoprotozoa of the genus Babesia. Numerous species of Babesia exist worldwide. An increased incidence of babesiosis is described, especially in North America. The babesial organism spends the majority of its life cycle within the erythrocyte of the definitive host, resulting in hemolysis, with or without systemic complications.

DIAGNOSIS

Definitive diagnosis depends on direct visualization of the organism on blood smear or polymerase chain reaction. A positive serologic antibody test indicates exposure with or without active infection.

THERAPY

Antiprotozoal drugs, antimicrobials, and supportive care are the mainstays of babesiosis therapy.

PROGNOSIS

Prognosis depends on the severity of disease, which in turn depends on both organism and host factors. Clinical syndromes associated with a poorer prognosis include red biliary syndrome, acute renal failure, acute respiratory distress syndrome, neurologic dysfunction, acute pancreatitis, cardiac dysfunction, and hypoglycemia.

Endocrine predictors of mortality in canine babesiosis caused by Babesia canis rossi

This prospective, cross-sectional, observational study was designed to determine the association between the hormones of the pituitary-adrenal and pituitary-thyroid axes and outcome in dogs with naturally occurring Babesia canis rossi babesiosis. Ninety-five dogs with canine babesiosis were studied and blood samples were obtained from the jugular vein in each dog prior to treatment at admission to hospital. Serum cortisol, adrenocorticotrophic hormone (ACTH), thyroxine, free thyroxine and thyrotropin (TSH) concentrations were measured. Diagnosis was confirmed by polymerase chain reaction and reverse line blot and dogs infected with Babesia canis vogeli or Ehrlichia canis were excluded. Three outcomes were defined: hospitalization with subsequent death (n=7); hospitalization followed by recovery (n=56); and treatment as an outpatient (n=32). Serum cortisol and ACTH concentrations were significantly higher in the dogs that died, compared to hospitalized dogs that survived and compared to dogs treated as outpatients. Serum T4 and free T4 concentrations were significantly lower in the dogs that died, compared to the hospitalized dogs that survived and compared to dogs treated as outpatients. Serum TSH concentrations were not significantly different between any of the groups. Mortality was significantly associated with high cortisol and high ACTH concentrations and with low T4 and fT4 concentrations in dogs suffering from B. canis rossi babesiosis.

Clinico-pathological findings and coagulation disorders in 45 cases of canine babesiosis in Spain

A retrospective study of clinical cases of babesiosis in dogs examined at the Veterinary Teaching Hospital, Rof Codina, from January 2003 to October 2004 is presented. The diagnosis was confirmed by direct observation of large piroplasms in stained blood smears. Dogs with concurrent diseases were excluded from the study. Clinical signs, complete blood count, serum biochemistry and hemostasis profiles were obtained. The observed clinical signs were due to hemolytic anemia and inflammatory responses but the most relevant clinico-pathological findings were related to alterations in hemostasis. All dogs presented with thrombocytopenia and 20% had disseminated intravascular coagulation syndrome. Anemia of variable severity was observed in most of the dogs.

Capillary and venous Babesia canis rossi parasitaemias and their association with outcome of infection and circulatory compromise

This observational study of 100 dogs naturally infected with Babesia canis rossi determined whether severity of parasitaemia was associated with outcome of infection and documented the relative distribution of parasitised red blood cells (pRBC) in capillary and venous circulation. The association between increased parasitaemias and outcome with a clinically compromised circulation was also investigated. Outcome was defined as either hospitalisation with death, or hospitalisation with eventual recovery or treatment as an outpatient. Dogs were enrolled if large babesias were found on stained thin capillary blood smears made from an ear prick. Thin venous smears were prepared from jugular or cephalic blood. Parasitaemias were manually counted and expressed as the percent pRBC. Ten dogs died, 50 recovered after hospitalisation and 40 were treated as outpatients. Venous sampling site did not affect venous parasitaemia (P=0.6). Both capillary and venous parasitaemias of dogs that died were significantly higher than those of dogs that recovered after hospitalisation (P=0.002) and dogs that were treated as outpatients (P<0.0001). When assessing the whole group, capillary parasitaemia (median 0.61%, range <0.05-71.6%, interquartile range (IQR) 0.22-3.75%) was significantly higher than venous parasitaemia (median 0.14%, range 0-30.6%, IQR 0.046-0.52%) with P<0.0001. The 21 dogs with a clinically compromised circulation were more likely to die (P<0.0001) and had significantly higher capillary (median 5.98%, range 0.09-71.6%, IQR 2.44-19.41%) and venous (median 2.81%, range <0.05-30.6%, IQR 0.17-9.03%) parasitaemias than the 79 dogs with a clinically normal circulation (capillary median parasitaemia 0.38%, range <0.05-12.87%, IQR 0.16-1.42%; venous median parasitaemia 0.096%, range 0-6.13%, IQR <0.05-0.33%; P<0.0001). This study shows that high parasitaemia is significantly associated with death in B c rossi infected dogs. The previous clinical suspicion that capillary parasitaemias are usually higher than venous parasitaemias is confirmed. Thus capillary samples are the most appropriate diagnostic samples. Prior observations that a clinically compromised circulation is associated with death are confirmed. Despite the highly significant association between compromised circulation and higher parasitaemia, it is thought unlikely that parasite burden is the sole trigger for circulatory collapse.

The South African form of severe and complicated canine babesiosis: clinical advances 1994-2004

Babesia (canis) rossi infection is common in dogs in South Africa, and frequently causes severe, life-threatening disease. Acidemia, persistent hyperlactatemia, hemoconcentration, elevated creatinine, cerebral babesiosis, pulmonary edema and pancreatitis are all associated with mortality rates above 30%, compared with overall mortality of 12% in admitted cases. Although half the admitted cases are severely anemic, hemoconcentration is associated with far higher mortality. Cerebral babesiosis is uncommon, but carries a poor prognosis. The pathological mechanism has been suggested to be endothelial cell damage and necrosis, followed by segmental microvascular necrosis with perivascular edema and hemorrhage. Renal involvement in babesiosis resembles the functional renal failure of sepsis. Hypotension is common, and other cardiovascular disturbances have been documented. Cerebellar ataxia, rhabdomyolysis and pancreatitis are recently identified complications. While the previous categorization into "severe" (life-threatening anemia) and "complicated" (complications not directly attributable to anemia) disease has proved useful, the distinction is artificial and probably unnecessary. An updated approach to classification is suggested, aimed at grouping animals by severity and prognosis, and using simple measures, such as clinical collapse and abnormal breathing, as much as possible. Although inflammatory mechanisms are undoubtedly important in the pathophysiology of babesiosis, there can be little doubt that tissue hypoxia plays a major role in the disease process.