Histopathological changes in sheep experimentally infected with Babesia ovis

A review of Babesiosis caused by Babesia ovis in small ruminants

Babesiosis is a significant tick-borne disease that impacts both domestic and wild animals, as well as humans, with its prevalence being particularly high in tropical and subtropical areas. Among small ruminants, Babesia ovis is a leading cause of babesiosis, especially in areas where Rhipicephalus bursa ticks are prevalent. The transmission of the disease occurs through tick bites, imposing a considerable economic strain on livestock industries in regions where it is prevalent. Clinical manifestations of the disease include hemolytic anemia, fever, jaundice, lethargy, anorexia, weight loss, and, in some cases, hemoglobinuria. A key aspect of babesiosis pathogenesis is the oxidative stress it induces in the host. For diagnosis, polymerase chain reaction (PCR) has emerged as the most sensitive and specific method, surpassing traditional diagnostic approaches like blood smears and serological testing. The treatment of choice for B. ovis infections in sheep is imidocarb dihydrochloride, which is administered in divided doses of 2 mg/kg. This treatment has proven effective in eradicating the parasite without relapse. Alternative treatments, such as aromatic diamidines, are associated with several drawbacks, including adverse effects and incomplete parasite clearance. Currently, diminazene aceturate and imidocarb dipropionate are widely employed babesiacidal drugs. Efforts to prevent and control babesiosis focus primarily on tick management, the use of resistant livestock breeds, and vaccination. Tick control strategies have evolved significantly, moving from traditional chemical dips to the use of systemic acaricides and self-treatment devices. Furthermore, non-chemical interventions, such as environmental management and selective breeding for tick resistance, are increasingly recognized as vital components of a comprehensive prevention strategy. This review provides an in-depth examination of the life cycle, epidemiology, risk factors, diagnostic methods, treatment options, and prevention strategies for B. ovis infection in small ruminants.

Experimental infection of purebred Saanen goats high pathogenicity and virulence of Babesia aktasi

Small ruminant babesiosis remains a neglected disease despite causing significant economic losses to sheep and goat herds in many regions around the world. The pathogenesis and clinical manifestations of ovine babesiosis are well-known, but there is a lack of information regarding caprine babesiosis. Since the discovery of the first Babesia spp. in 1888, several species/subspecies/genotypes, including Babesia aktasi, have been described. Our recent molecular survey revealed that the parasite is highly prevalent (22.5%) in indigenous goats from Mediterranean region of Türkiye. The aim of this experimental study was to determine the pathogenicity and virulence of B. aktasi in immunosuppressed (n = 5) and immunocompetent (n = 7) purebred Saanen goats. The goats were experimentally infected with fresh B. aktasi infected blood, and examined for clinical, parasitological, hematological, and serum biochemical findings throughout the infection. Following the parasite inoculation, intra-erythrocytic parasites were detected from the 1st day post-infection, followed by an increase in rectal temperature and parasitemia. The parasitemia was detected ranging from 4.3% to 33.5% in the immunosuppressed group, while it was 2.1% to 7.6% in the immunocompetent. Severe clinical symptoms characterized by anemia, jaundice, and hemoglobinuria developed in both groups. A statistically significant inverse correlation was observed between the increase in parasitemia and RBC, WBC, HCT, and Hb values in the goats compared to pre-infection levels. Values of AST, ALT, GGT, Total bilirubin, and Albumin showed a significant increase, with all the immunosuppressed goats dying on the 4th and 7th days post-infection, while four out of seven immunocompetent goats died on between 6-8th days. Severe edema in the lungs, frothy fluid in the trachea, jaundice in the subcutaneous and mesenteric fat, and dark red urine were detected in necropsy. The results obtained in this study demonstrated that B. aktasi was highly pathogenic to purebred Saanen goats. Current work assures valuable insights into the pathogenesis and virulence of B. aktasi and serves as a foundation for future studies to develop effective control strategies against caprine babesiosis.

Evaluation of cardiovascular biomarkers and histopathological alterations in cattle naturally infected by Babesia bigemina

Hemolytic anemia and secondary hypoxia are characteristics of naturally occurring Babesia bigemina infection in cattle. The anemic phase comes with cardiovascular insufficiency due to hypoxia-induced system dysfunction; but to date there is no description of cardiac damage in the infected animals. Therefore, this study was undertaken to investigate hematological parameters, biomarkers of cardiac function and D-dimer in 13 cattle infected with B. bigemina which were unresponsive to standard treatment. The animals were necropsied and the cardiac tissue was examined for histopathologic alterations. A significant parasitemia burden-dependent increase in the cardiac biomarkers and D-dimer level were recorded in the infected cattle compared to the control animals. Thrombocytes count was also significantly lower in the infected animals than the control. Both macroscopic and microscopic hemorrhage, mononuclear infiltrates, and myocardial necrosis were the evident histopathologic findings. These findings suggest that B. bigemina infection can potentially induce cardiac dysfunction in cattle. Furthermore, mechanistic studies should be conducted to understand the mechanisms beyond cardiac complications.

Disorders in blood circulation as a probable cause of death in dogs infected with Babesia canis

Introduction

The purpose of the study was to investigate post-mortem changes in dogs infected with Babesia canis and to establish the probable cause of death of the affected animals.

Material and Methods

Cadavers of six dogs that did not survive babesiosis were collected. Necropsies were performed and samples of various organs were collected for histological examination.

Results

Necropsies and histological examinations revealed congestion and oedemata in various organs. Most of the dogs had ascites, hydrothorax or hydropericardium, pulmonary oedema, pulmonary, renal, hepatic, and cerebral congestion, and necrosis of cardiomyocytes.

Conclusion

These results suggested disorders in blood circulation as the most probable cause of death. However, the pulmonary inflammatory response and cerebral babesiosis observed in some of these dogs could also be considered possible causes of death. This study also showed a possible role for renal congestion in the development of renal hypoxia and azotaemia in canine babesiosis.

Transmission of Babesia ovis by different Rhipicephalus bursa developmental stages and infected blood injection

In this report, the transmission efficacy of Babesia ovis, the principal causative agent of ovine babesiosis, was studied by infestation of lambs with different Rhipicephalus bursa stages or by injection of infected blood. Infected blood injection induced acute babesiosis in splenectomized lambs, while only mild clinical signs were observed in intact animals. Both splenectomized and intact lambs developed high antibody titer, detectable for at least 180 days post infection. Infestation of splenectomized and intact lambs with infected tick larvae did not induce clinical babesiosis or specific serum response in any of the examined animals. Similarly, infestation of one splenectomized lamb with partially-fed infected R. bursa males did not induce any clinical response or seroconversion. Nymph infestation caused a mild clinical response followed by specific seroconversion, in one out of five lambs. All animals infested with infected unfed adults (males and females) showed mild-to-severe clinical signs 8 to 12 days post infestation. The acute phase was followed by a marked seroconversion. Our results indicate that the principal transmission of B. ovis is performed by adult R. bursa ticks, and that the host reaction can last as long as 6 months following the acute infection.

Histological and ultrastructural studies of renal lesions in Babesia canis infected dogs treated with imidocarb

Histological and electron microscopic examinations of the kidneys of 8 dogs suffering from fatal, naturally acquired Babesia canis infection and nephropathy are presented. Seven animals were treated with imidocarb dipropionate on average 4.5 days prior to death. Severe anaemia was present only in 2 cases. Degenerative histological changes observed mostly in the proximal convoluted tubules included vacuolar-hydropic degeneration, necrosis and detachment of renal tubular epithelial (RTE) cells from the basement membrane. Necrotic debris occasionally formed acidophilic casts within the tubules. In some cases, necrosis of the whole tubule was observed. Haemoglobin casts in the tubules and haemoglobin droplets in RTE cells seldom appeared. No significant histological changes were seen in the glomeruli. Ultrastructural lesions in RTE cells included nuclear membrane hyperchromatosis, karyopyknosis, karyolysis, swelling or collapse of mitochondria with fragmentation of cristae and vacuolar-hydropic degeneration in the endoplasmic reticulum and microvilli. Nuclear oedema was also observed. Many RTE cells exhibiting necrosis collapsed. Vacuolar-hydropic degeneration and necrosis were also observed in the glomerular and interstitial capillary endothelium. The severe acute tubular necrosis described in this study is probably the result of hypoxic renal injury. Systemic hypotension leading to vasoconstriction in the kidneys might be the most important cause of renal hypoxia in B. canis infections, but anaemia may also contribute to inadequate oxygenation. Imidocarb should be applied with caution in patients with possible renal involvement until further data become available on its potential nephrotoxicity in dogs.

Shared features in the pathobiology of babesiosis and malaria

The pathobiology of malaria has been extensively studied in humans but many questions remain, especially regarding fulminant disease associated with Plasmodium falciparum infection. Babesiosis, recognized since biblical times as an important disease of livestock and more recently as an emerging health problem in humans, is caused by related intraerythrocytic protozoa with a similar pathogenesis and clinical course. Recent studies of cytokine activation and erythrocyte cytoadherence in babesiosis and malaria have exploited these similarities to provide new insights into malaria pathobiology. Continued investigation of similarities and differences in the pathogenesis of babesiosis and malaria should lead to additional fundamental insights for both conditions.

Clinical, clinico-pathological and serological studies of Babesia ovis in experimentally infected sheep

Clinical, clinico-pathological and serological studies were performed in sheep experimentally infected with Babesia ovis. Acute babesiosis occurred in all the lambs infested with adult Rhipicephalus bursa ticks and in one lamb infested with the larvae. The rate of parasitaemia and the degree of anaemia were not correlated. Decrease in the packed-cell volume ranged from 30 to 40%. Parasitized erythrocytes were not observed to block capillaries in the brain, which explained the absence of nervous symptoms in acute babesiosis. The kidneys were the most severely affected organs, exhibiting acute glomerulonephritis. The lesions observed were suggestive of vascular alteration and vascular stasis, leading to anoxia of the tissues. A disseminated intravascular coagulation (DIC) syndrome was recorded in sheep infected with babesiosis. A marked increase in the enzymes of the transaminase groups, mainly aspartate aminotransferase (AST), was observed. Enzymatic changes (increases in AST, alanine aminotransferase (ALT) and lactic dehydrogenase (LDH) and decreases in sorbitol dehydrogenase (SDH), alkaline phosphatase (ALP) and malic enzyme (MEZ)), decreases in total proteins and albumin, and increases in urea and creatinine might reflect the degree of severity of the damage to the liver and kidney tissues. Most of the lambs (85%) that were infested with larvae, and all lambs infested with adult R. bursa ticks, reacted serologically to B. ovis antigen. The serological reactions following infestation with the larvae occurred much later than those following infestation with the adult stage. The lambs which were infested with larvae showed mild clinical reactions when challenged by infected R. bursa adults, as compared with the reactions to the challenge in naive control animals. The serological findings, in addition to the fact that one splenectomized lamb reacted to larval infestation with acute ovine babesiosis, show that the preimaginal stages of R. bursa can transmit B. ovis, usually causing a sub-clinical disease. It is suggested that infections derived from preimaginal ticks in the winter can preimmunize sheep for the subsequent more severe infections derived from adult ticks in the summer. Furthermore, in the absence of a reliable vaccine against B. ovis, grazing flocks in the enzootic regions should be exposed to the preimaginal stages during their activity period (October-February) before exposure to the adult ticks in spring and summer (April-July).

Some epizootiological and clinical aspects of ovine babesiosis caused by Babesia ovis--a review

The study shows a close relationship between incidence of ovine babesiosis caused by Babesia ovis and the activity period and distribution area of the vector tick Rhipicephalus bursa. The most important factor limiting the distribution of this tick is a decrease in humidity. In general, it is absent from areas with an average annual rainfall of less than about 300 mm. The rate of parasitaemia and the degree of anaemia were not correlated. Decrease of the packed-cell volume ranged from 30 to 40%. Parasitized erythrocytes were not observed to block capillaries in the brain, which explained the absence of nervous symptoms in acute babesiosis. The kidney was the most severely affected organ, exhibiting acute glomerulonephritis. The lesions observed were suggestive of vascular alteration and vascular stasis, leading to anoxia of the tissues. A disseminated intravascular coagulation (DIC) syndrome was recorded in sheep infected with babesiosis. Biochemical studies revealed possible damage to the liver and kidneys. Most of the lambs (85%) that were infested with larvae, and all lambs infested with adult R. bursa ticks reacted serologically to B. ovis antigen. The serological reactions following infestation with the larvae occurred much later than those following infestation with the adult stage. Both transovarial and transstadial transmission of the parasite were demonstrated. A study of antibodies to B. ovis using IFAT in hoggets and ewes revealed high serological prevalence, i.e., 88.9% in ewes and 84.5% in hoggets. No marked seasonal fluctuation was observed. The serological findings, in addition to the fact that one splenectomised lamb reacted to larval infestation with acute ovine babesiosis, show that the preimaginal stages of R. bursa occurring in the winter can transmit B. ovis, usually causing a sub-clinical disease. This might play a major role in pre-immunizing and strengthening the premunition of the sheep against the main spring challenge by the adult ticks. The sub-clinical reactions are probably due to the low infection rate of the preimaginal stages of R. bursa by B. ovis parasites.