Emergency management of severe anemia due to presumptive Babesia vogeli in a Puppy: Whole blood transfusion and doxycycline monotherapy

Introduction

Babesia vogeli is a large, mild to moderate pathogenic subspecies of Babesia that infects dogs (Solano-Gallego et al., 2016, Sharma et al., 2025) [13,12] . It is morphologically characterized by large intraerythrocytic, piriform (teardrop-shaped, 2.5 × 4.0 μm) piroplasms occurring either single or in pairs. The parasite is primarily transmitted by the brown dog tick, Rhipicephalus sanguineus, an endophilic and monotrophic species commonly inhabiting human dwellings, kennels, and environments where dogs and people live in close contact. While B. vogeli infection generally produces mild to moderate subclinical disease in adult dogs, severe clinical manifestations may occur, particularly in young, debilitated, or immunocompromised animals. The pathogenicity in puppies is often exacerbated by the immaturity of their immune systems and lower splenic reserve, resulting in poor clearance of infected erythrocytes. Management of canine babesiosis typically involves specific antiprotozoal agents such as imidocarb dipropionate or diminazene aceturate, often combined with doxycycline or clindamycin to enhance therapeutic efficacy and control concurrent tick-borne infections (Solano-Gallego et al., 2016, Karasov et al., 2022) [13,6] . However, in cases presenting with severe hemolytic anemia-where the Packed Cell Volume (PCV) falls below critical thresholds-emergency stabilization with whole blood transfusion is essential to restore oxygen-carrying capacity and improve immediate survival, particularly in critically anemic puppies (Aravindh & Jacob, 2021; Dadke & Galdhar, 2021; Reddy et al., 2024) [1,5,10] . The present report describes the successful emergency management of a life-threatening presumptive B. vogeli infection in a two-month-old puppy using whole-blood transfusion and doxycycline monotherapy. This case highlights the importance of early intervention and the efficacy of targeted supportive care in managing critically anemic pediatric patients.

Case Presentation

A 2-month-old male mixed-breed puppy weighing 2.2 kg was presented to the Small Animal Clinics-Outpatient Medicine Unit, VCRI, Tirunelveli, with a history of progressive weakness, inappetence and blanched mucous membranes. Upon physical examination, the puppy was dull, weak and recumbent. Clinical findings included marked pallor of the mucous membranes and icterus. Vital parameters revealed a body temperature of 35°C, heart rate of 120 beats/min, and a respiratory rate of 15 breaths/min. A heavy infestation of Rhipicephalus sanguineus ticks was also noted. Hematological evaluation confirmed life-threatening anemia with a Packed Cell Volume (PCV) of 10% and hemoglobin of 3.3 g/dL. Severe thrombocytopenia (40,000 /µL) was also evident, consistent with hemolytic anemia. This hematological alteration is consistent with clinicopathological findings reported in canine babesiosis (Bilwal et al., 2017; Rafaj et al., 2006) [2,9] . Peripheral blood smear examination by Giemsa stain demonstrated large forms of intraerythrocytic piroplasms (2.5 × 4.0 µm) morphologically consistent with Babesia spp. Given the local prevalence and vector presence, a presumptive diagnosis of Babesia vogeli was made. Upon identifying the critical status of the patient, an emergency whole-blood transfusion was prioritized. A total of 100 mL of blood was collected aseptically from the jugular vein of a clinically healthy, adult donor dog into a CPDA-1 anticoagulant blood collection bag (Fig. 1). The required transfusion volume was calculated using the following formula:

Where V is the volume to be transfused (mL) and BW is the body weight (kg). Due to the emergency nature of the case and the fact that this was the patient's first lifetime transfusion, cross-matching was not performed. However, transfusion protocols recommend compatibility testing whenever feasible to prevent transfusion reactions and transmission of blood-borne pathogens (Stegeman et al., 2003; Aravindh & Jacob, 2021) [14,1] . Transfusion was initiated at a conservative rate of six drops per minute for the first 10 minutes under close hemodynamic monitoring to detect any acute hemolytic reactions. Upon ensuring stability, the infusion rate was increased to 20 drops per minute, allowing administration of a total of 45 mL of whole blood over one hour. Significant clinical improvement, including a return of appetite and increased activity, was observed within 24 hours post-transfusion. A follow-up complete blood count on Day 4 revealed a PCV increase to 28%, confirming a successful hematological response. Post-transfusion therapeutic management consisted of doxycycline administered intravenously at 5 mg/kg once daily for five days, followed by oral administration at 10 mg/kg for an additional 21 days. Adjunctive therapy included intravenous fluid therapy, hematinics and nutritional supplementation. While standard protocols often combine doxycycline with imidocarb dipropionate, this patient showed complete clinical and hematological recovery with doxycycline monotherapy and supportive care. The puppy was monitored for seven days post-treatment, showing sustained recovery and no recurrence of anemia.

Discussion

Canine babesiosis is a globally significant and potentially lifethreatening hemoprotozoan disease (Selim et al., 2022) [11] . While Babesia rossi is traditionally viewed as the most virulent species, B. vogeli-transmitted by the ubiquitous brown dog tick Rhipicephalus sanguineus-is increasingly recognized for its severe clinical impact on specific populations (Coralic et al., 2018) [4] . Although this protozoan is described as a mildly pathogenic or subclinical subspecies in adults (Koster et al., 2015) [7] , this case corroborates findings by Wang et al. (2018) [15] that B. vogeli can induce fatal hemolytic crises in pediatric, debilitated, or immunocompromised hosts.The diagnosis in this patient was based on the triad of clinical presentation, severe hematological derangement, and microscopic identification of large piroplasms. While PCR confirmation was not available to definitively differentiate B. vogeli from other large Babesia species, the morphology and vector association strongly support the presumptive diagnosis. The observed anemia was likely multifactorial, resulting from direct parasite-induced erythrocyte membrane damage, increased osmotic fragility and immune-mediated hemolysis (Boozer & Macintire, 2003) [3] . A critical intervention in this case was the emergency wholeblood transfusion. In patients presenting with a PCV as low as 10%, immediate restoration of oxygen-carrying capacity is essential to prevent tissue hypoxia and potential multi-organ failure. The marked clinical improvement observed within 24 hours post-transfusion highlights that stabilization of the red blood cell mass is often the most crucial step in managing acute pediatric cases of severe babesiosis. Tick-borne blood pathogen infections in puppies pose a significant therapeutic challenge due to immature hepatic and renal function, increased susceptibility to drug toxicity, and frequent presentation with severe anemia. Although standard treatment for Babesia vogeli typically includes imidocarb dipropionate or diminazene aceturate, their use in very young dogs warrants caution. In the present case, doxycycline monotherapy was utilized to achieve pathogen control while minimizing drug-related risks. Doxycycline exhibits anti-Babesia activity, likely through the inhibition of apicoplast protein synthesis, a mechanism similar to its action in other apicomplexan parasites (Mittal et al., 2025) [8] . When combined with aggressive supportive management, including blood transfusion, doxycycline appeared sufficient to assist in clinical stabilization and hematologic recovery. This approach is particularly relevant in puppies and in settings where access to potent antiprotozoals may be limited or contraindicated. Clinical and experimental evidence supports this strategy. Wongtawan et al. (2024) [16] reported PCR-confirmed clearance of tick-borne pathogens following doxycycline monotherapy, with marked improvement in hematological profiles. Similarly, experimental studies have demonstrated pathogen reduction with doxycycline treatment (Zhang et al., 2023) [17] . However, it is important to note that without PCR confirmation of clearance, it is difficult to determine if the parasite was eliminated or if the dog achieved a carrier state while clinical signs resolved. Overall, doxycycline monotherapy (10 mg/kg/day for 28 days), combined with appropriate supportive care, represents a rational and safer therapeutic option for puppies with suspected tick-borne blood pathogen infections, particularly when conventional antiprotozoal regimens pose safety risks.

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