Prophylactic activity of imidocarb against experimental infection with Babesia canis

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.

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.

Canine vector-borne diseases in Brazil

Canine vector-borne diseases (CVBDs) are highly prevalent in Brazil and represent a challenge to veterinarians and public health workers, since some diseases are of great zoonotic potential. Dogs are affected by many protozoa (e.g., Babesia vogeli, Leishmania infantum, and Trypanosoma cruzi), bacteria (e.g., Anaplasma platys and Ehrlichia canis), and helminths (e.g., Dirofilaria immitis and Dipylidium caninum) that are transmitted by a diverse range of arthropod vectors, including ticks, fleas, lice, triatomines, mosquitoes, tabanids, and phlebotomine sand flies. This article focuses on several aspects (etiology, transmission, distribution, prevalence, risk factors, diagnosis, control, prevention, and public health significance) of CVBDs in Brazil and discusses research gaps to be addressed in future studies.

Therapeutic and prophylactic efficacy of imidocarb dipropionate on experimental Babesia ovis infection of lambs

The objective of this study was to evaluate the therapeutic and prophylactic efficacy of imidocarb dipropionate (IMDP) against babesiosis and to determine specific antibodies against Babesia ovis in experimentally infected lambs. Thirty-six 6-month-old splenectomized lambs were used. The lambs were randomly divided into six groups with six animals each, and were intravenously inoculated with 50 mL B. ovis-infected erythrocytes as follows: group I (therapy group) was treated with IMDP (1.2 mg/kg body weight) starting on the day of onset of clinical signs of babesiosis after the inoculation; group II (untreated control animals) was not treated with any therapeutic treatment after the inoculation; groups III, IV, V and VI (prophylaxis groups) were administered IMDP (2.4 mg/kg body weight) 1, 2, 3 and 4 weeks before the inoculation, respectively. The animals were housed in a tick-proof room with water and food ad libitum up to the 30th day post-inoculation (PI). The lambs were monitored from the first day PI by recording the manifestation of clinical disease, rectal temperature, and the degree of parasitaemia. All the lambs became infected with B. ovis, except five animals from group III, which were treated 1 week prior to experimental infection. Other animals showed signs of acute clinical babesiosis. The animals treated with IMDP (group I) were able to clear the parasite from the blood circulation after 48 h post-treatment. The recrudescence of B. ovis was observed in two lambs 7 days after treatment, and they were treated with the second similar dose of the drug. Six lambs (1, 1, 2 and 2 lambs in group III, IV, V and VI, respectively) from the prophylaxis groups died within 7-17 days after showing high parasitaemia and clinical symptoms of the disease. Regardless of the clinical symptoms, 83.30% and 66.66% of the lambs which were administered IMDP 1-2 and 3-4 weeks before, were determined to be protected against the virulent field strain of B. ovis.

Canine babesiosis: A Brazilian perspective

Canine babesiosis is highly endemic in Brazil, caused by Babesia canis and Babesia gibsoni, both transmitted by Rhipicephalus sanguineus ticks. The present review argues for a more adequate method of characterizing the Babesia species infecting dogs and cats in different Brazilian endemic zones. It advocates for a comprehensive understanding of the biology of R. sanguineus ticks under Brazilian conditions in order to define the more effective preventive strategies against canine babesiosis and calls for partnerships between the public and private sectors for research on canine babesiosis and other vector-borne diseases in Brazil.

Clinicopathological changes and effect of imidocarb therapy in dogs experimentally infected with Babesia canis

In this study one spleen-intact dog (A) and two splenectomised dogs (BSE, CSE) were infected with Babesia canis. All animals developed an acute disease characterised by fever, haemoglobinuria and anaemia, the latter being more severe in the splenectomised dogs. Fever and parasitised red blood cells were detected for three days after imidocarb treatment in the splenectomised animals. Haematological abnormalities included regenerative anaemia, thrombocytopenia and leukopenia (due to neutropenia and lymphopenia) in the acute phase, soon followed by leukocytosis, neutrophilia and left shift a few days later. Acute hepatopathy was detected in all dogs with elevated ALT activity, which was more seriously altered in the splenectomised dogs. Diffuse changes in liver structure and hepatomegaly were seen by ultrasonography. Liver biopsy and histology revealed acute, non-purulent hepatitis in the splenectomised dogs. Both splenectomised dogs were successfully cured after collection of 400 ml highly parasitised blood, proving that large-amount antigen production is possible with rescuing the experimental animals. Whole blood transfusion, imidocarb and supportive care with infusions, antipyretics, glucocorticoids and diuretics were applied. The spleen-intact dog clinically recovered after receiving supportive treatment, with no imidocarb therapy. Microbial infections developed in both splenectomised animals (BSE: haemobartonellosis, CSE: osteomyelitis caused by Escherichia coli), probably as a consequence of immunosuppression after splenectomy and glucocorticoid therapy.

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.

Pharmacokinetics of imidocarb dipropionate in horses after intramuscular administration

The objective of this study was to determine the pharmacokinetic behaviour of imidocarb in horses following a single i.m. injection at the dose commonly administered to treat Babesia caballi infections or to prevent babesiosis. Eight horses were injected i.m. with a single dose of 2.4 mg imidocarb dipropionate/kg bwt and blood, faecal, urine and milk samples were collected. For imidocarb determination, a high-performance liquid chromatographic method (HPLC) was used after weak cation-exchange solid phase, or liquid-liquid, extraction procedures. Twelve hours after treatment, no detectable plasma concentrations were recorded in any of the treated animals. The distribution and elimination patterns of the drug suggested that it is quickly sequestrated in some storage tissues and remains in the body for a long time. Its prolonged presence in the body may confer a reservoir effect to imidocarb in some tissues, therefore making it undetectable in the plasma of animals but sufficient to produce its described therapeutic and prophylactic activities.

Prophylactic treatment of experimental canine babesiosis (Babesia canis) with doxycycline

Doxycycline provided satisfactory prophylaxis against experimental infection with a highly pathogenic strain of Babesia canis. Rectal temperature, parasitaemia, packed cell volume and serology were monitored for evaluation of the prophylactic effect. Although a daily dose of 5 mg kg-1 of doxycycline did not completely prevent clinical disease, symptoms remained moderate and a full recovery was obtained within 1 week. At a dose of 20 mg kg-1 day-1 no clinical symptoms were observed, but asymptomatic infection could not be ruled out.