Development of Babesia gibsoni in the midgut of larval tick, Rhipicephalus sanguineus

Babesia gibsoni infection in Italy: a cross sectional study of 607 blood samples belonging to dogs that needed a molecular analysis investigation (2016-2019)

Babesia gibsoni (B. gibsoni) infection was sporadically described in Europe. In Italy, in particular, it was detected by PCR analysis only in one dog with unclear source of infection, while it has never been found in molecular studies involving more subjects. The aim of this retrospective, cross-sectional study was to determine the presence and the proportion of B. gibsoni infected dogs in a convenient Italian canine population. Babesia spp PCR analysis reports of canine blood samples collected from January 2016 to December 2019 were selected from the San Marco veterinary laboratory database and evaluated. Piroplasms PCR analysis was performed on 18S rRNA gene and positive samples were sequenced. Available data about signalment, living area and season of diagnosis were evaluated and statistically analyzed. The studied canine population had a median age of 62 months (interquartile range, IQR: 72.5) and was composed of male/female purebred and mixed breed dogs. Through sequencing, B. canis (26/40, 65%), B. vogeli (7/40, 17.5%), B. gibsoni (6/40, 15%) and B. vulpes (1/40, 2.5%) infections were reported. The proportion of B. gibsoni infected dogs in the described population was of 0.99%. The infection resulted more likely in male (6/6, 100%), purebred (5/6, 83.3%) dogs with median age of 40.5 months (IQR:32.3). In one case, the clinical signs and parasitemia appeared after a dogfight with a cohabitant infected dog. No other plausible sources of infection were detected. Likely, this could be considered the first autochthonous B. gibsoni infection case documented in Italy. Our results underline the need of considering B. gibsoni not only an exotic, random and rare cause of disease for dogs in Italy, but a possible emerging pathogen to take into account during diagnostic and epidemiological investigations, in symptomatic as well as in asymptomatic patients.

ACVIM consensus statement on the diagnosis of immune-mediated hemolytic anemia in dogs and cats

Immune-mediated hemolytic anemia (IMHA) is an important cause of morbidity and mortality in dogs. IMHA also occurs in cats, although less commonly. IMHA is considered secondary when it can be attributed to an underlying disease, and as primary (idiopathic) if no cause is found. Eliminating diseases that cause IMHA may attenuate or stop immune-mediated erythrocyte destruction, and adverse consequences of long-term immunosuppressive treatment can be avoided. Infections, cancer, drugs, vaccines, and inflammatory processes may be underlying causes of IMHA. Evidence for these comorbidities has not been systematically evaluated, rendering evidence-based decisions difficult. We identified and extracted data from studies published in the veterinary literature and developed a novel tool for evaluation of evidence quality, using it to assess study design, diagnostic criteria for IMHA, comorbidities, and causality. Succinct evidence summary statements were written, along with screening recommendations. Statements were refined by conducting 3 iterations of Delphi review with panel and task force members. Commentary was solicited from several professional bodies to maximize clinical applicability before the recommendations were submitted. The resulting document is intended to provide clinical guidelines for diagnosis of, and underlying disease screening for, IMHA in dogs and cats. These should be implemented with consideration of animal, owner, and geographical factors.

The Complexity of Piroplasms Life Cycles

Although apicomplexan parasites of the group Piroplasmida represent commonly identified global risks to both animals and humans, detailed knowledge of their life cycles is surprisingly limited. Such a discrepancy results from incomplete literature reports, nomenclature disunity and recently, from large numbers of newly described species. This review intends to collate and summarize current knowledge with respect to piroplasm phylogeny. Moreover, it provides a comprehensive view of developmental events of Babesia, Theileria, and Cytauxzoon representative species, focusing on uniform consensus of three consecutive phases: (i) schizogony and merogony, asexual multiplication in blood cells of the vertebrate host; (ii) gamogony, sexual reproduction inside the tick midgut, later followed by invasion of kinetes into the tick internal tissues; and (iii) sporogony, asexual proliferation in tick salivary glands resulting in the formation of sporozoites. However, many fundamental differences in this general consensus occur and this review identifies variables that should be analyzed prior to further development of specific anti-piroplasm strategies, including the attractive targeting of life cycle stages of Babesia or Theileria tick vectors.

Molecular evidence for the transovarial passage of Babesia gibsoni in Haemaphysalis hystricis (Acari: Ixodidae) ticks from Taiwan: a novel vector for canine babesiosis

BACKGROUND

Babesia gibsoni is the predominant tick-borne protozoan blood parasite affecting dogs throughout the Oriental region. Babesia gibsoni is transmitted by Haemaphysalis longicornis, whereas a similar role has been suggested for Rhipicephalus sanguineus. Haemaphysalis longicornis does not occur in Taiwan, but R. sanguineus is widely distributed on dogs. However, clinical cases of babesiosis are mainly restricted to the northern part of the island. The discrepancy between tick distribution and clinical cases stimulated us to investigate the tick species distribution on dogs in northern Taiwan, with the aim to identify the local vector for canine babesiosis.

METHODS

Ticks were collected from stray dogs or free ranging pet dogs in northern Taiwan between 2015 and 2017 and, after identification, were tested for the presence of tick-borne Babesia parasites using PCR and reverse line blot (RLB) hybridisation. Moreover, engorged ticks collected from the dogs were incubated at 28 °C to allow them to oviposit. Their subsequent larval progeny was also examined by PCR/RLB.

RESULTS

A total of 1085 ticks collected from 144 stray dogs at different residential areas consisted of 5 different species: H. hystricis (n = 435), R. sanguineus (n = 582), R. haemaphysaloides (n = 43), Amblyomma testudinarium (n = 14) and Ixodes ovatus (n = 11) were identified. Babesia gibsoni DNA was detected in H. hystricis females (10.3%), males (7.0%) and in 2.6% of the nymphs. One R. sanguineus female and one A. testudinarium female tick also carried B. gibsoni DNA. DNA of B. gibsoni was demonstrated in 11 out of 68 (16.2%) batches of larval ticks derived from engorged H. hystricus ticks only. Babesia vogeli DNA was detected only in R. sanguineus females (2.6%) and males (2.4%). DNA of B. vogeli was detected in 13 out of 95 (13.7%) batches of larval ticks derived from engorged R.sanguineus females.

CONCLUSIONS

Babesia gibsoni DNA was detected in the larval progeny of H. hystricis ticks only, whereas B. vogeli was restricted to the larvae of R. sanguineus. This provides evidence for transovarial passage of B. gibsoni in H. hystricis and evidence that this tick does act as the local vector for this parasite on dogs in northern Taiwan where most cases of babesiosis are reported. The vectorial capacity of R. sanguineus for babesiosis is probably restricted to the transmission of B. vogeli only.

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.

Babesia gibsoni genotype Asia in dogs from Brazil

Babesia gibsoni was first recognized in India in 1910. Analysis of 18S rRNA has shown that there are at least three distinct isolates that are morphologically identical. Although organisms similar to B. gibsoni have been identified in peripheral blood smears from one dog in Brazil, this isolate has not been molecularly characterized. Accordingly, we obtained blood samples from 16 dogs with intraerythrocytic inclusion bodies. DNA was extracted and amplified with primers that detect a segment of the 18S rRNA gene of the Babesia genus. Amplicons of the expected size for B. gibsoni were observed in 4 of the 16 dogs. The sequence of the 18S rRNA yield a 460 base pair segment that had a 99% homology with the B. gibsoni genotype Asia 1. Our findings suggest that the small piroplasm that naturally infects dogs in Brazil is B. gibsoni genotype Asia.

Geographic distribution of babesiosis among dogs in the United States and association with dog bites: 150 cases (2000-2003)

OBJECTIVE

To identify the geographic distribution of babesiosis among dogs in the United States and determine, for dogs other than American Pit Bull Terriers (APBTs), whether infection was associated with a recent dog bite.

DESIGN

Retrospective study.

ANIMALS

150 dogs.

PROCEDURE

Canine blood samples submitted to the North Carolina State University Vector-Borne Disease Diagnostic Laboratory between May 2000 and October 2003 for which results of a Babesia-specific polymerase chain reaction assay were positive were identified, and breed and geographic origin of dogs from which samples were obtained were recorded. History and hematologic abnormalities for dogs that were not APBTs were recorded, and possible associations with a recent dog bite were examined.

RESULTS

Dogs positive for Babesia DNA were located in 29 states and 1 Canadian province (Ontario). Babesia gibsoni was the most commonly detected species, with B gibsoni DNA detected in blood samples from 131 of 144 (91%) dogs. Of the 131 dogs positive for B gibsoni DNA, 122 (93%) were APBTs. Of the 10 dogs positive for Babesia canis vogeli DNA, 6 were Greyhounds. In dogs other than APBTs, there was an association between having recently been bitten by another dog, particularly an APBT, and infection with B gibsoni.

CONCLUSIONS AND CLINICAL RELEVANCE

Results document an expansion of the known geographic range for babesiosis among dogs in the United States. Testing for babesiosis should be pursued in dogs with clinicopathologic abnormalities consistent with immune-mediated hemolytic anemia or thrombocytopenia, particularly if there is a history of a recent dog bite.

Serosurvey of AntiBabesia Antibodies in Stray Dogs and American Pit Bull Terriers and American Staffordshire Terriers From North Carolina

Stray dogs (n=359) and kennel dogs (n=149) from North Carolina were tested for evidence of antiBabesia antibodies. AntiBabesia antibodies were detected in 21/359 and 22/149 of the stray and kennel dogs, respectively. A total of 57 dogs from both groups were tested for babesiasis by light microscopy and polymerase chain reaction (PCR). Babesia deoxyribonucleic acid (DNA) was detected in 3/28 of the stray dogs and 14/29 of the kennel dogs. When Babesia DNA was detected by PCR, the species-specific PCR results differed from the Babesia species antibody titer results in 6/17 of the PCR-positive dogs. There was no association between antiBabesia antibodies and the presence of ticks. There are currently Babesia gibsoni epizootics affecting American pit bull terrier kennels.

Morphological studies on the extracellular structure of the midgut of a tick, Haemaphysalis longicornis (Acari: Ixodidae)

In the present study, morphological observations on the extracellular structures found on the apical surface of the midgut epithelium, known as the peritrophic membrane (PM) or glycocalyx, are described in Haemaphysalis longicornis females and larvae. These structures have been hypothesized to provide protection to the microvilli of epithelial cells of the digestive tract. Our aim was to determine whether the extracellular structures are important in the digestion of the blood meal and/or as a protection against infection or injury. The PM was detectable in the midgut of engorged larvae by electron microscopy, but not in engorged females. However, a PM-like structure, stainable with toluidine blue, was observed in females by light microscopy. From the results of confocal laser scanning and electron microscopic observations with wheat germ agglutinin (WGA lectin) staining for chitin of the PM, however, the structure was clearly recognized. The structure in the female is likely to be PM because staining with WGA lectin in the presence of GlcNAc indicates the presence of chitin and various morphologies of PM have been reported in insects and ticks. These results show morphologically that different types of PM-like structure are formed in larvae and females of H. longicornis.

Babesia gibsoni infection in three dogs in Victoria

Small intraerythrocytic parasites were observed in the blood of three related male American Pit Bull Terriers. Two of the dogs, both less than 1-year-old, were anaemic at the time of initial examination and the third, an adult and sire of the two younger dogs, had a normal haemogram and low parasitaemia. The morphological appearance of the erythrocyte inclusions, analysis of a 450-bp region of the 18S rRNA gene and antibody titres provided evidence that this parasite was Babesia gibsoni, a species not previously reported in Australia.