Indirect immunofluorescent antibody (IFA), latex agglutination (IA), and enzyme immunoassay (EIA) methods were compared for evaluation of the serum antibody responses of dogs experimentally and naturally exposed to spotted fever-group rickettsiae. Selected sera (obtained on days 1, 42, 53, 124, 145, 236, 255, 264, and 292) were examined from three 8-month-old female Beagles inoculated with Rickettsia rickettsii on days 34 and 250 of the study. A second group of dogs comprised three 8-month-old female Beagles inoculated with R montana on days 34 and 102. Subsequently, these dogs were inoculated with R rickettsii on day 250. Serum samples were obtained from the second group of dogs on days 1, 96, 103, 132, 180, 215, 292, and 494. A third group consisted of 21 naturally exposed dogs, from which sequentially obtained serum samples were available, and which had clinical signs compatible with Rocky Mountain spotted fever. Clinical signs of disease in dogs of the third group resolved after treatment with tetracycline (22 mg/kg of body weight, Po, q 8 h) was instituted. At least 2 sequentially obtained serum samples from each dog were tested. In general, the first sample was obtained just prior to treatment and the convalescent serum samples were obtained at weekly or greater intervals thereafter. For correlation and reactivity data, an IFA test for IgG/IgM (using heavy and light chains-specific conjugate) was used as the reference standard for comparison of results with those of the other tests,

The vascular permeability of the ocular fundus, alterations in the coagulation system, and plasma concentrations of thromboxane B2 (TXB2) and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) were studied in dogs following intradermal inoculation with 5 x 10(5) TCID50 of Rickettsia rickettsii. Twenty-four to 48 hours after the onset of fever and rickettsemia, multifocal areas of retinal vasculitis were evident, which corresponded to areas of altered vascular permeability demonstrated by fluorescein angiography. The number and intensity of retinal vessels with sodium fluorescein leakage peaked during the second week after inoculation, and retinal vascular permeability remained altered during the third week of infection, well past the phase of clinical and clinicopathologic recovery. Development of retinal vasculitic foci was associated with thrombocytopenia, increased concentrations of circulating fibrinogen, and slight prolongation of activated partial thromboplastin time. Increased concentrations of fibrin/fibrinogen degradation products were detected in 4 of 9 dogs. Despite the degree of vascular endothelial damage evident on fluorescein angiographic and histologic studies in these dogs, plasma TXB2 and 6-keto-PGF1 alpha concentrations were not increased.

The kinetics of specific IgM and IgG antibody response was characterized in four 9-month-old Beagles after inoculation of 2 x 10(2) plaque-forming units (PFU) of Sheila Smith strain of Rickettsia rickettsii. Immunoglobulin M antibodies were first detected by indirect immunoflorescence on postinoculation (PI) day 9, peaked by PI day 20, and were no longer detectable by PI day 80. Immunoglobulin G antibodies became detectable between PI days 22 and 28, peaked by PI day 42, and decreased gradually through PI day 130. Subsequent challenges with R rickettsii on PI days 216 (2 x 10(2) PFU/dog) and 1,029 (5 x 10(4) tissue culture infective dose [TCID50]/dog) resulted in slightly different serologic responses. The initial challenge exposure failed to increase the concentration of IgG antibodies and induced only low concentrations of IgM antibodies. After the second challenge inoculation, IgM antibodies were not detectable and the concentration IgG antibodies increased slightly. Clinical abnormalities and seroconversion were documented in control dogs following each challenge exposure. Examination of acute and convalescent serum samples from 55 dogs in which Rocky Mountain spotted fever was suspected clinically suggested that sole evaluation of IgM antibodies in acute-phase serum would result in inaccurate diagnoses because of false-positive and -negative results. Use of a composite conjugate that detects IgM and IgG antibodies to R rickettsii appears to be satisfactory for diagnostic purposes; however, concurrent quantitation of IgM antibodies may facilitate serodiagnosis in a select group of dogs in which a four-fold increase in convalescent antibody titer is not detected by use of the composite conjugate. With the exception of a dog with a serum antibody titer of 1:8,192, we were unable to detect IgM or IgG antibodies in CSF samples from 9 dogs with experimentally and 3 dogs with naturally acquired infections.

Amblyomma hebraeum, 60CO irradiation of nymphs failed to attenuate Cowdria ruminatium

Objective: The abundance of tick populations in South Africa represents a probable risk for both animal and human health. Rickettsia spp. and Borrelia spp. are well-known agents of emerging human tick-borne infectious diseases worldwide. Nevertheless, the epidemiology of their infec¬tions has been underreported in South Africa. Therefore, this study aimed to profile zoonotic Rickettsia and Borrelia species from ticks infesting domesticated animals in the Eastern Cape, South Africa. Materials and Methods: Morphological and molecular identification techniques were conducted on 1,200 tick samples collected from domestic animals before screening for the target bacterial pathogens. The molecular identification of the tick samples was based on the amplification of the 12S rRNA mitochondrial Deoxyribonucleic acid. At the same time, those of Rickettsia and Borrelia species were carried out by amplifying fragments of gltA and ompB genes for Rickettsia and flaB gene for Borrelia spp. Thereafter, the positive amplicons for Rickettsia ompB were sequenced and further analyzed. Borrelia PCRs were negative; therefore, sequencing could not be performed. Results: Eight species of ticks belonging to three genera; Rhipicephalus, Amblyomma, and Haemaphysalis, were identified. A total of 27% (320/1,200) samples were confirmed positive for Rickettsia, of which 23% (74/320) were positive for ompB genes. Phylogenetic analysis of ompB revealed a high homology to rickettsial reference strains from GenBank, with no positive result for Borrelia. The generated sequences showed homology with R. africae-KX227790 (100%), R. parkeri-KY113111 (99.8%), R. peacockii (99.3%), and R. slovaca-JX683122 (99.1%) representative sequences in GenBank. Conclusion: The findings from this study revealed that ticks harbored Rickettsia species with possible zoonotic potential. [J Adv Vet Anim Res 2024; 11(2.000): 254-263]

De 106 Rattus norvegicus capturados no Estado do Rio de Janeiro, observou-se que 25,47% estavam parasitados por Grahamella legeri sp. n. na zona rural a prevalência foi de 53,84% e na zona urbana de 16,25%. A riquetsia foi identificada em esfregaços de sangue periférico, corados pelo método Giemsa, sendo analisada morfológica e biologicamente. As tentativas de transmissão do parasito para diferentes espécies de mamíferos, por inoculaçâo de sangue infectado, só tiveram êxito para R. norvegicus; nestes se provocou aumento da parasitemia conseqüente à esplenectomia ou a injeções de dexametasona. Registrou-se a evolução de quadro clínico de anemia induzida pela infecção com G. legeri. Não houve êxito no cultivo da riquetsia em meio de cultura tido como específico para o gênero. Discutiu-se a posição sistemática, concluíndo-se pela impropriedade da denominação de Grahamella muris Leger, 1913, pelo que se propôs o nome Grahamella legeri, em homenagem a André Legér.

<p>It was observed that 25.47% of the Rattus norvegicus examined from the Rio de Janeiro State, Brazil, were infected by Grahamella legeri sp. n. being 53.84% in the rural and 16.25% in the urban zone. The rickettsia found in the blood smears and organ imprints stained by the method of Giemsa was studied morphologically and biologically. The experimental transmission with infected blood was obtained only between individuals of the same species and the enhancement of its virulence by the stress of the host was obtained with Dexa-metazone or by splenectomy. The cultivation of the parasite was attempted in an artificial medium, specific for Grahamella spp. The pathogenicity of the organism was demonstrated. Its systematic position was discussed and it was concluded that it represents a new species of Rickettsiales, Bartonellaceae, so for improperly denominated Grahamella muris Leger, 1913, for which it is proposed the name Grahamella legeri in honor of André Leger.</p> | De 106 Rattus norvegicus capturados no Estado do Rio de Janeiro, observou-se que 25,47% estavam parasitados por Grahamella legeri sp. n. na zona rural a prevalência foi de 53,84% e na zona urbana de 16,25%. A riquetsia foi identificada em esfregaços de sangue periférico, corados pelo método Giemsa, sendo analisada morfológica e biologicamente. As tentativas de transmissão do parasito para diferentes espécies de mamíferos, por inoculaçâo de sangue infectado, só tiveram êxito para R. norvegicus; nestes se provocou aumento da parasitemia conseqüente à esplenectomia ou a injeções de dexametasona. Registrou-se a evolução de quadro clínico de anemia induzida pela infecção com G. legeri. Não houve êxito no cultivo da riquetsia em meio de cultura tido como específico para o gênero. Discutiu-se a posição sistemática, concluíndo-se pela impropriedade da denominação de Grahamella muris Leger, 1913, pelo que se propôs o nome Grahamella legeri, em homenagem a André Legér.

Ticks (Acari: Ixodidae) are obligatory hematophagous ectoparasites of a variety of vertebrate hosts and play an important role in the transmission and ecology of infectious pathogens causing diseases in humans and animals worldwide. Sixty-eight species of ticks exist in Brazil, and at least 23 are found parasitizing wild birds. This number is increasing with the advent of new studies highlighting the underestimated role of birds in the life cycle of these arthropods. In South America, many of these ticks are involved in epidemiology of the life-threatening spotted fever diseases caused by bacteria from the genus Rickettsia (Rickettsiales: Rickettsiaceae). The aim of this paper is to present up-to-date knowledge about the bird-tick fauna of Brazil and their association with rickettsioses. The available literature concerning ticks on birds and tick-borne diseases related to these ticks in Brazil has been revised. It could be concluded that birds play a primary role in life cycles of various tick species, especially during immature stages (larvae and nymphs). The best known is a bird-tick fauna from the Atlantic Forest and from Brazilian savannah called Cerrado in southern and central Brazil, respectively. On the other hand, the knowledge about bird tick parasitism from other Brazilian biomes such as the Amazon, Caatinga, Pantanal and Pampas regions is very scarce and requires further study. Moreover, no studies about the role of birds as mobile hosts for spreading ticks to new areas exist, nor has their role in the natural life cycle of Rickettsia been thoroughly examined.