The Mixed Acid-Base Disturbances of Severe Canine Babesiosis

Babesiosis: Current status and future perspectives in Pakistan and chemotherapy used in livestock and pet animals

Babesiosis is a protozoal disease affect livestock and pet animals such as cattle, buffaloes, sheep, goats, horses, donkeys, mules, dogs, and cats. It causes severe economic losses in livestock as well as in pet animals. A large number of dairy animals are imported in order to fulfill the demands of milk, milk, meat and its products. In addition, different pet animals are transported from Pakistan to various parts of the world, therefore, it is important to identify the current status and distribution of babesiosis throughout Pakistan in order to control the disease and draw attention for future research, diagnosis, treatment and control of this diseases. No work has been done on a complete review on up-to-date on blood protozoal disease burden in Pakistan. This article will provide about the complete background of babesiosis in ruminants, equines and pet animals, its current status, distribution, vectors in Pakistan and allopathic and ethnoveterinary treatments used against babesiosis. Babesiosis may be subclinical (apparently normal) and may be clinical with acute to chronic disease and sometimes fatal. Babesia is found and develops inside the erythrocytes (red blood cells). Clinically, it causes fever, fatigue, lethargy, pallor mucus membranes, malaise, cachexia, respiratory distress, jaundice, icterus, hemolytic anemia, hemoglobinuria, lymphadenopathy, chollangocytitis, hepatomegaly, and splenomegaly. Chemotherapy for babesiosis includes Imidocarb dipropionate, Diaminazine aceturate Atovaquone and Bupravaquone, Azithromycin, Quinuronium sulfate and Amicarbalidesio-thionate are most widely used. Supportive therapy includes multivitamins, fluid therapy, antipyretics intravenous fluids, and blood transfusions are used if necessary. In addition, there are certain ethnoveterinary (homeopathic) ingredients which having anti-babesial activity. As the resistance against these drugs is developing every day. New more specific long-lasting drugs should be developed for the treatment of Babesiosis. Further studies should be done on disease genome of different species of Babesia for vaccine development like malarial parasites.

Lung pathology of natural Babesia rossi infection in dogs

A proportion of Babesia rossi infections in dogs are classified as complicated and one of the most lethal complications is acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Most dogs that die succumb within 24 hours of presentation. The pulmonary pathology caused by B. rossi in dogs has not been described. The aim of this study was to provide a thorough macroscopic, histological and immunohistochemical description of the lung changes seen in dogs naturally infected with B. rossi that succumbed to the infection. Death was invariably accompanied by alveolar oedema. Histopathology showed acute interstitial pneumonia characterised by alveolar oedema and haemorrhages, with increased numbers of mononuclear leucocytes in alveolar walls and lumens. Intra-alveolar polymerised fibrin aggregates were observed in just over half the infected cases. Immunohistochemistry showed increased numbers of MAC387- and CD204-reactive monocyte-macrophages in alveolar walls and lumens, and increased CD3-reactive T-lymphocytes in alveolar walls, compared with controls. These histological features overlap to some extent (but far from perfectly) with the histological pattern of lung injury referred to as the exudative stage of diffuse alveolar damage (DAD) as is quite commonly reported in ALI/ARDS.

Blood Parasites and Health Status of Hibernating and Non-Hibernating Noctule Bats (Nyctalus noctula)

Co-existence of bats with a wide range of infectious agents relates to their co-evolutionary history and specific physiology. Here, we examined blood samples collected during hibernation and the post-hibernation period to assess the influence of trypanosomes and babesias on the health status of 50 Noctule bats (Nyctalus noctula) using nested PCR. The impact of blood parasites on health was assessed by analysis of haematology and blood chemistry parameters in 21 bats. Prevalence of trypanosomes (Trypanosoma dionisii and T. vespertilionis) and babesia (Babesia vesperuginis) was 44% and 8%, respectively. Analysis of blood parameters indicated impact of babesia on acid–base balance. Blood chemistry parameters showed a significant decrease in total dissolved carbon dioxide and bicarbonate, increased anion gap, and no change in blood pH, suggesting compensated metabolic acidosis. Adverse effects of babesia were only apparent in hibernating bats. Our results suggest differences in the pathogenicity of trypanosomes and babesia in bats. While trypanosomes in general had no significant impact on the health status, we observed alterations in the blood acid–base balance in Babesia-infected bats during hibernation. Despite being infected, Babesia-positive bats survived hibernation without showing any clinical signs.

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.

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.

Prospective evaluation of plasma lactate parameters for prognosticating dogs with shock

OBJECTIVE

To determine whether admission venous plasma lactate concentration, serially calculated lactate variables, or the Acute Patient Physiologic and Laboratory Evaluation (APPLE_fast ) score could discriminate hospital survivors from non-survivors in dogs presenting to the emergency department with clinical signs of shock.

DESIGN

Prospective case series performed over a 24-month period.

SETTING

Large urban private teaching hospital.

ANIMALS

Seventy-one dogs admitted to the ICU with initial peripheral venous plasma lactate concentration > 2.5 mmol/L and clinical and hemodynamic parameters consistent with shock.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Heart rate, systolic blood pressure, temperature, initial venous plasma lactate, and APPLE_fast score were recorded at admission. Lactate concentrations were serially recorded at predefined time points and used to calculate lactate variables, including lactime (time lactate > 2.5 mmol/L), lactate clearance ([lactate_initial - lactate_delayed ]/ lactate_initial × 100), and LAC_AREA (area under the lactate concentration versus time curve). Primary outcome was survival to discharge. Overall survival rate was 61%. Admission plasma lactate did not differ between groups (P = 0.28). Lactime was shorter in survivors vs non-survivors (P = 0.03). Lactate clearance at hours (h) 1, 4, 10, and 16 was greater in survivors vs non-survivors (P < 0.05). Final plasma lactate clearance differed between groups (P < 0.05). LAC_AREA at time intervals 1 to 4 hours, 4 to 10 hours, 10 to 16 hours, and 16 to 24 hours was larger in non-survivors vs survivors (P < 0.05). Total LAC_AREA did not differ between groups (P = 0.51). Admission APPLE_fast was not different between survivors and non-survivors (P = 0.16).

CONCLUSIONS

While neither single APPLE_fast nor admission plasma lactate concentration could discriminate between hospital survivors and non-survivors, measures of lactate clearance can prognosticate survival in dogs with shock.

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.

Hyponatraemia and Syndrome of Inappropriate Antidiuretic Hormone Secretion in Non-azotaemic Dogs with Babesiosis Associated with Decreased Arterial Blood Pressure

Introduction

A previous study on canine babesiosis showed low serum tonicity in affected dogs, which may result from syndrome of inappropriate antidiuretic hormone secretion (SIADH). This endocrine disorder was recognised in human malaria which is considered a disease with similar pathogenesis to canine babesiosis. The aim of this study was to investigate the occurrence of SIADH in babesiosis-afflicted dogs.

Material and Methods

Serum and urinary sodium and urine specific gravity (USG) were determined in dogs with babesiosis. Mean arterial pressure (MAP) was measured at the beginning of the clinical examination. Serum tonicity and osmolality were calculated. Correlations were calculated between MAP and serum and urinary sodium concentrations, USG, serum tonicity, and calculated serum osmolality.

Results

Statistically significant correlations were observed between MAP and tonicity, calculated osmolality, USG, and serum and urinary sodium concentrations in non-azotaemic dogs. In three non-azotaemic dogs SIADH was recognised.

Conclusion

SIADH develops in non-azotaemic dogs with babesiosis. It is probably associated with decreased blood pressure in infected dogs. Thus, it seems that in fact it may be appropriate vasopressin secretion in canine babesiosis as a protective mechanism in hypotension which leads to hypoxia and renal failure in affected dogs.

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.

Development and validation of a multiplex, real-time PCR assay for Babesia rossi and Babesia vogeli

Canine babesiosis is caused by tick-transmitted intraerythrocytic protozoan parasites occurring worldwide. In southern Africa, babesiosis is caused by Babesia rossi and B. vogeli and is one of the most common and important infectious diseases affecting dogs. There is no reliable, rapid and sensitive method for the detection of these parasites, especially when parasitaemia is low. The aim of this study was to develop a sensitive and specific multiplex TaqMan® MGB PCR assay for the diagnosis of canine babesiosis infections occurring in southern Africa, and to discriminate between Babesia rossi and B. vogeli. The fitness of purpose of the assay was to confirm diagnosis of suspect or clinical cases, and estimate prevalence of infection for research purposes. A total of 648 published sequences were used to design the assay. A set of group-specific canine Babesia spp. primers were designed to amplify a 117 nucleotide region of the 18S rRNA gene of all canine Babesia spp. Species-specific TaqMan® MGB probes were developed for B. rossi, B. vogeli, B. canis and B. gibsoni, but analytical validation was only performed for B. rossi and B. vogeli as a multiplex assay. The assay had a broad dynamic range and amplified B. rossi and B. vogeli efficiently (98.6% and 94.7% respectively). The assay was sensitive, with a 95% LOD of 10^-2.67% parasitized erythrocytes (PE) for B. rossi and 10^-2.03% PE for B. vogeli, and specific, with no cross reaction between B. rossi and B. vogeli and no detection of other haemoparasites that infect dogs, such as Ehrlichia canis and Anaplasma platys. Consistent repeatability within and between PCR runs was shown. This assay will be able to accurately and rapidly confirm babesiosis in canines and allow for treatment to be administered in the early stages of the disease, speeding up the recovery time in affected dogs.

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.

Clinical use of plasma lactate concentration. Part 2: Prognostic and diagnostic utility and the clinical management of hyperlactatemia

OBJECTIVE

To review the current literature pertaining to the use of lactate as a prognostic indicator and therapeutic guide, the utility of measuring lactate concentrations in body fluids other than blood or plasma, and the clinical management of hyperlactatemia in dogs, cats, and horses.

DATA SOURCES

Articles were retrieved without date restrictions primarily via PubMed, Scopus, and CAB Abstracts as well as by manual selection.

HUMAN AND VETERINARY DATA SYNTHESIS

Increased plasma lactate concentrations are associated with increased morbidity and mortality. In populations with high mortality, hyperlactatemia is moderately predictive in identifying nonsurvivors. Importantly, eulactatemia predicts survival better than hyperlactatemia predicts death. Consecutive lactate measurements and calculated relative measures appear to outperform single measurements. The use of lactate as a therapeutic guide has shown promising results in people but is relatively uninvestigated in veterinary species. Increased lactate concentrations in body fluids other than blood should raise the index of suspicion for septic or malignant processes. Management of hyperlactatemia should target the underlying cause.

CONCLUSION

Lactate is a valuable triage and risk stratification tool that can be used to separate patients into higher and lower risk categories. The utility of lactate concentration as a therapeutic target and the measurement of lactate in body fluids shows promise but requires further research.

Antiprotozoal treatment of canine babesiosis

Canine babesiosis is a tick-borne disease caused by several Babesia spp. which have different susceptebility to anti-protozoal drugs. A few drugs and drug combinations are used in the treatment of canine babesiosis often without complete parasite elimination leaving treated dogs as carriers which could relapse with clinical disease and also transmit infection further. Although the large form canine babesial species Babesia canis, Babesia vogeli and Babesia rossi are sensitive to the aromatic diamidines imidocarb dipropionate and diminazene aceturate, small form species such as Babesia gibsoni, Babesia conradae and Babesia vulpes (Theileria annae) are relatively resistant to these drugs and are treated with the combination of the hydroxynaphthoquinone atovaquone and the antibiotic azithromycin. Azithromycin and other antibiotics that have anti-protozoal properties target the apicoplast, a relict plastid found in protozoa, and exert a delayed death effect. The triple combination of clindamycin, diminazene aceturate and imidocarb dipropionate is also effective against B. gibsoni and used to treat atovaquone-resistant strains of this species. Novel drugs and the synergistic effects of drug combinations against Babesia infection should be explored further to find new treatments for canine babesiosis.

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.

First molecular detection of Babesia canis in dogs from Bosnia and Herzegovina

Babesia spp. are tick-transmitted protozoan haemoparasites of great economic, veterinary and medical impact worldwide. Herein we reported the very high prevalence of autochthonous babesiosis in symptomatic dogs from Bosnia and Herzegovina in the period from 2014 to 2016. Eighty dogs that did not leave the country were examined using parasitological and molecular analyses and babesiosis was diagnosed in 82.5% and 85.0% of them, respectively (p < 0.001). One species, Babesia canis was identified using molecular methodology (PCR and sequence analysis). Statistical analyses showed that epizootiological characteristics have no influence on the possibility of infection. Agglomerative hierarchical clustering (AHC) analyses used for comparing the symptoms and clinical signs of infection in dogs pointed out that a high degree of anemia, followed by thrombocytopenia (89%), lethargy (100%), loss of appetite (95%), fever (66%) and icterus (61%) was dominant. In addition, results of the statistical analysis performed showed that more dogs with no data of tick prophylaxis (70%) were found Babesia infected. Those results point to further intensified epizootic surveys in the territory of Bosnia and Herzegovina.

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.

Electron Microscopic Study of Canine Babesia Gibsoni Infection

Canine babesiosis is a tick-borne parasitic disease caused by the intraerythrocytic parasites, Babesia canis and Babesia gibsoni. A lethargic, weak, American Staffordshire Terrier (pit bull) dog, which had regenerative, normocytic, normochromic anemia, was shown by polymerase chain reaction analysis to be infected with B. gibsoni. Transmission electron microscopy of ethylenediamine tetraacetic acid–treated blood disclosed many well-preserved, intraerythrocytic babesia trophozoites. Four morphologic forms of babesia trophozoites are described (small spheres, small rods, irregular forms lacking pseudoinclusions, and large spheres having pseudoinclusions) and are compared with intraerythrocytic forms of B. canis and B. gibsoni described in other light and electron microscopic studies of in vivo and in vitro Babesia infections. This is the first detailed transmission electron microscopic study of canine B. gibsoni–infected red blood cells in North America.

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.

Hyperaldosteronism and its association with hypotension and azotaemia in canine babesiosis

BACKGROUND

The previous work on canine babesiosis revealed hypokalaemia and increased fractional excretion of potassium in infected dogs suggesting a role for aldosterone in the loss of potassium via the kidneys in affected dogs. Moreover, hypotension, which is one of the complications of canine babesiosis leading to renal failure, may induce secondary hyperaldosteronism.

ANIMALS AND METHODS

In this study, the serum aldosterone concentration was determined in 14 dogs infected with Babesia canis. The Mann-Whitney U test was used to compare serum aldosterone concentration and blood pressure between these dogs and 10 healthy dogs. Spearman's rank correlations between serum aldosterone concentration and blood pressure and between serum aldosterone and urea and creatinine concentrations were calculated.

RESULTS

Increased concentrations of aldosterone above reference intervals were observed in only 4 out of the 14 dogs. The results showed significantly (p < 0.05) higher serum aldosterone concentrations and lower blood pressures in infected dogs in comparison to healthy dogs, and significantly negative correlations between aldosterone concentration and systolic arterial pressure (r = -0.63), diastolic arterial pressure (r = -0.67) and mean arterial pressure (r = -0.65). Serum aldosterone concentration was also significantly correlated with serum urea concentration (r = 0.72), serum creatinine concentration (r = 0.69) and serum potassium concentration (r = -0.57).

CONCLUSION

The results of this study show hyperaldosteronism in some cases of canine babesiosis as a possible response to hypotension. However, both the hypotension and severe azotaemia observed in dogs infected with B. canis and associated hyperaldosteronaemia suggest that this response is insufficient.

A comparison of traditional and quantitative analysis of acid-base imbalances in hypoalbuminemic dogs

OBJECTIVE

To compare the traditional (HH) and quantitative approaches used for the evaluation of the acid-base balance in hypoalbuminemic dogs.

DESIGN

Prospective observational study.

SETTING

ICU of a veterinary teaching hospital.

ANIMALS

One hundred and five client-owned dogs.

MEASUREMENTS AND MAIN RESULTS

Jugular venous blood samples were collected from each patient on admission to determine: total plasma protein (TP), albumin (Alb), blood urea nitrogen (BUN), glucose (Glu), hematocrit (HCT), Na(+) , Cl(-) , K(+) , phosphate (Pi ), pH, PvCO2, bicarbonate (HCO3 (-) ), anion gap (AG), adjusted anion gap for albumin (AGalb ) or phosphate (AGalb-phos ), standardized base excess (SBE), strong ion difference (SID), concentration of nonvolatile weak buffers (Atot ), and strong ion gap (SIG). Patients were divided in 2 groups according to the severity of the hypoalbuminemia: mild (Alb = 21-25 g/L) and severe (Alb ≤20 g/L). All parameters were compared among groups. Patients with severe hypoalbuminemia showed significant decrease in TP (P = 0.011), Atot (P = 0.050), and a significant increase in adjusted AG (P = 0.048) and the magnitude of SIG (P = 0.011) compared to animals with mild hypoalbuminemia. According to the HH approach, the most frequent imbalances were simple disorders (51.4%), primarily metabolic acidosis (84.7%) associated with a high AG acidosis. However, when using the quantitative method, 58.1% of patients had complex disorders, with SIG acidosis (74.3%) and Atot alkalosis (33.3%) as the most frequent acid-base imbalances. Agreement between methods only matched in 32 cases (kappa < 0.20).

CONCLUSIONS

The agreement between the HH and quantitative methods for interpretation of acid-base balance was poor and many imbalances detected using the quantitative approach were missed using the HH approach. Further studies are necessary to confirm the clinical utility of using the quantitative approach in the decision-making process of the severely ill hypoalbuminemic patients.

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.

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.

A prospective, randomized comparison of Oxyglobin (HB-200) and packed red blood cell transfusion for canine babesiosis

OBJECTIVE

To establish the efficacy of Oxyglobin (HB-200) in canine babesiosis and compare it to standard therapy, packed red blood cell transfusion (pRBCT) with respect to improvements in specific parameters of blood gas, acid-base, blood pressure, and subjective evaluations.

DESIGN

Prospective, randomized, clinical trial.

SETTING

Onderstepoort Veterinary Academic Hospital.

ANIMALS

Twelve dogs (8-25 kg) naturally infected with Babesia rossi and a hematocrit of 0.1-0.2 L/L (10-20%).

INTERVENTIONS

Treatment groups were randomized to receive either 20 mL/kg of Oxyglobin or pRBCT over 4 hours via a central venous catheter. Transfusions were followed by lactated Ringer's solution infusion. Rectal temperature, femoral arterial and mixed venous blood sampling, oscillometric blood pressure, and subjective assessment of patient status (habitus), and appetite were performed at time points 0, 1, 4, 8, 24, 48, and 72 hours.

MAIN RESULTS

Dogs presented with a hypoalbuminemic alkalosis; hyperchloremic, dilutional acidosis; normotensive tachycardia; pyrexia; depression; and anorexia. Both treatments produced similar results, with the exception of significant differences in pH (4 h); PCO(2) (4 h); hemoglobin (8 h, 24 h); mean arterial pressure (48 h); albumin (4 h, 8 h); habitus (8 h, 48 h); and appetite (24 h). Arterial O(2) content was higher for pRBCT than Oxyglobin at 72 hours, but central venous PO(2) did not differ between groups or over time and was consistently subnormal.

CONCLUSIONS

Oxyglobin provides similar overall improvements to pRBCT in dogs with anemia from babesiosis, with respect to blood gas, acid-base and blood pressure, although patients receiving packed cells tended to have more rapid normalization of habitus and appetite.

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.

Humoral immunity and reinfection resistance in dogs experimentally inoculated with Babesia canis and either treated or untreated with imidocarb dipropionate

It is proposed that the chronic asymptomatic carrier state produced by Babesia canis infection could make dogs more resistant against subsequent infections. This suggests that treatment with imidocarb dipropionate, which removes the organism, can make dogs more susceptible to reinfection in a short period of time. Ten male and female dogs of approximately 4-5 months of age were inoculated with B. canis. Half of them received treatment with imidocarb dipropionate (7 mg/kg) on days 15 and 27 post-infection and the other half were untreated. All the animals were examined using clinical and laboratory methods (CBC, platelet counts and serological study by indirect immunofluorescence test) for a 6-month period. Antibodies were first detected on day 7 post-injection and remained at high levels (1:2560) over the period in the non-treated group. This result was significantly different (P<0.001) from the treated group in which antibodies titers declined after day 34 post-infection. Six months later, after a homologous challenge infection only the dogs of treated group showed parasitaemia, thrombocytopenia and splenomegaly, which was significantly different (P<0.05) from the non-treated group. The sterilizing treatment with imidocarb dipropionate was effective in clearing the infection, but inhibited the maintenance of protective antibodies, making the animals more susceptible to reinfection.