Wild carnivores, domestic dogs and ticks: shared parasitism in the Brazilian Cerrado.

The increase of contact between natural and rural areas is prominent in Brazil, due to agricultural activities and concern with the environmental conservation. In this context, domestic animals, wild fauna and humans are exposed to mutual exchange of parasites, microorganisms and diseases. We studied tick parasitism of wild carnivores and domestic dogs, and the environmental of questing ticks, in extensive cattle ranch areas intermingled with natural vegetation, and in a natural reserve, both in a region of Cerrado biome, Midwestern Brazil. From 2008 to 2015, we inspected 119 wild carnivores from nine species, and collected six tick species (Amblyomma sculptum, Amblyomma ovale, Amblyomma dubitatum, Amblyomma tigrinum, Dermacentor nitens and Rhipicephalus microplus). The most numerous and infested hosts were Cerdocyon thous, Lycalopex vetulus, Chrysocyon brachyurus, Puma concolor and Conepatus amazonicus. From 139 domestic dogs, we collected A. sculptum, Rhipicephalus sanguineus and R. microplus. From vegetation, samplings resulted in A. sculptum, A. dubitatum, A. ovale, Amblyomma rotundatum and R. microplus, with dominance of A. sculptum. Domestics and wild animals presented high overlapping of infestations by A. sculptum, a generalist and anthropophilic tick species. This tick is the most important vector of the Brazilian spotted fever, a lethal human disease. This fact elicits attention and requires efforts to monitor the presence of pathogens vectored by ticks circulating in this type of agroecosystem, including in other regions of the Brazil, because the most of the natural vegetation remaining have been increasingly immersed in pastures and agricultural matrix.

Correction to: Occurrence of anti-Leptospira spp. antibodies in Rhipidomys spp. from a forest fragment of the Brazilian Cerrado.

The original version of this article unfortunately contains an error. Vanessa do Nascimento Ramos was not included in the original article as one of the contributors. The name is now included in the authorgroup.

Occurrence of anti-Leptospira spp. antibodies in Rhipidomys spp. from a forest fragment of the Brazilian Cerrado.

Leptospirosis is a zoonotic disease of world importance, and its transmission depends on the interaction between humans and animals. Given the necessity to investigate potential hosts of Leptospira spp., this study verified the prevalence of different serovars in the species of Rhipidomys spp., a widespread sigmodont rodent in Brazil. The studied population originates from a semi-evergreen forest located in the county of Uberlândia, in the state of Minas Gerais. The microscopic agglutination test (MAT) was performed with 14 serovars. Thirteen out of the 43 wild rodents captured showed a positive agglutination reaction, with a greater prevalence of the serovars Pyrogenes, Copenhageni, and Canicola. This study found a prevalence of 30.3% anti-Leptospira spp. antibodies; all positive animals were reactive to more than one serovar.

Comparative evaluation of infected and noninfected Amblyomma triste ticks with Rickettsia parkeri, the agent of an emerging rickettsiosis in the New World.

The distribution of Rickettsia parkeri in South America has been associated with Amblyomma triste ticks. The present study evaluated under laboratory conditions two colonies of A. triste: one started from engorged females that were naturally infected by R. parkeri (designated as infected group); the other started from noninfected females (designated as control group). Both colonies were reared in parallel for five consecutive generations. Tick-naïve domestic rabbits were used for feeding of each tick stage and generation. R. parkeri was preserved by transstadial maintenance and transovarial transmission in A. triste ticks for five consecutive generations, because all tested larvae, nymphs, and adults from the infected group were shown by PCR to contain rickettsial DNA. All rabbits infested by larvae, nymphs, and adults from the infected group seroconverted, indicating that these tick stages were all vector competent for R. parkeri. Expressive differences in mortality rates were observed between engorged nymphs from the infected and control groups, as indicated by 65.9% and 92.4% molting success, respectively. Our results indicate that A. triste can act as a natural reservoir for R. parkeri. However, due to deleterious effect caused by R. parkeri on engorged nymphs, amplifier vertebrate hosts might be necessary for natural long-term maintenance of R. parkeri in A. triste.

In vitro isolation from Amblyomma ovale (Acari: Ixodidae) and ecological aspects of the Atlantic rainforest Rickettsia, the causative agent of a novel spotted fever rickettsiosis in Brazil.

Recently, a novel human rickettsiosis, namely Atlantic rainforest spotted fever, was described in Brazil. We herein report results of a survey led around the index case in an Atlantic rainforest reserve in Peruibe municipality, southeastern Brazil. A Rickettsia parkeri-like agent (Rickettsia sp. Atlantic rainforest genotype) and Ricketsia bellii were isolated from adult Amblyomma ovale ticks collected from dogs. Molecular evidence of infection with strain Atlantic rainforest was obtained for 30 (12.9%) of 232 A. ovale adult ticks collected from dogs. As many as 88.6% of the 35 examined dogs had anti-Rickettsia antibodies, with endpoint titres at their highest to R. parkeri. High correlation among antibody titres in dogs, A. ovale infestations, and access to rainforest was observed. Amblyomma ovale subadults were found predominantly on a rodent species (Euryoryzomys russatus). From 17 E. russatus tested, 6 (35.3%) displayed anti-Rickettsia antibodies, with endpoint titres highest to R. parkeri. It is concluded that Atlantic rainforest genotype circulates in this Atlantic rainforest area at relatively high levels. Dogs get infected when bitten by A. ovale ticks in the forest, and carry infected ticks to households. The role of E. russatus as an amplifier host of Rickettsia to A. ovale ticks deserves investigation.

Experimental evaluation of birds as disseminators of the cosmopolitan tick Rhipicephalus sanguineus (Acari: Ixodidae).

Rhipicephalus sanguineus is believed to be the most widespread tick species of the world and its dissemination seems to rely on the diffusion of its main host, the dog. Empirical observations indicate that several bird species in urban areas regularly steal dog food. Such circumstances create a chance for R. sanguineus ticks to climb on birds and carry ticks to another site. In this work we evaluated experimentally the likelihood of birds (chicks) to either feed and/or carry R. sanguineus ticks from an infested site to another and to infest a host (rabbit) in the new location. Chicks were not suitable hosts for R. sanguineus ticks. Not a single adult tick engorged on chicks, yield as well as weight of engorged larvae and nymphs were very low and feeding period of these ticks was very long. However, a few larvae and, chiefly, nymphs were delivered to a new location either mechanically or after attachment and engorging total or partially on chicks. A few of these ticks fed successfully on rabbits. Further evidence on the capacity of birds to introduce R. sanguineus into non-infested dog settings should be provided by systematic examination of birds from urban areas, close to tick infested households.

A surrogate life cycle of Amblyomma ovale Koch, 1844.

As ticks spend most of their time off-host, the environment is a major selective force of these parasites. In fact, human impact on landscapes has favored a minority of tick species which became well-known pests. However, this is an ongoing process and novel pests may arise. We herein report a surrogate life cycle of a neotropical tick species, Amblyomma ovale, and which may be related to an increased risk of human rickettsiosis. Under natural conditions, adults of this tick species feed on carnivores and exhibit non-nidicolous ambush behavior, whereas larvae and nymphs feed on small rodents and birds. In an anthropized spot within an Atlantic rainforest reserve of Brazil, an A. ovale population exhibited a nidicolous behavior with all 3 tick stages feeding on the dog. This dog's infestation was outstandingly high, and it displayed the highest anti-Rickettsia titers and harbored Rickettsia-infected ticks.

Capybaras and ticks in the urban areas of Uberlândia, Minas Gerais, Brazil: ecological aspects for the epidemiology of tick-borne diseases.

In Brazil capybara, the biggest existing rodent species, and associated tick species, Amblyomma cajennense and Amblyomma dubitatum, are undergoing an unplanned host and parasite population expansion in both urban and rural areas. However, scientific information about such issue, particularly in urban areas, is scanty. Such rodent and ticks are associated in some municipalities, particularly in southeastern Brazil, with the transmission of the highly lethal Rickettsia rickettsia caused spotted-fever. In this study ecological aspects related to the establishment and expansion of capybaras and ticks in urban areas of Uberlândia, Minas Gerais State, Brazil were evaluated. For this purpose, capybara and tick abundance in four urban areas and an ecological reserve was determined. Abundance of capybaras varied between areas and over the sampling period and these differences were related to human activities. A positive correlation was found between capybara and tick abundance, however, the tick species had an uneven distribution within the municipality and environmental factors rather than host availability were blamed for such. On the whole these observations show that capybara populations in urban areas are associated to high environmental infestation of ticks and the increased risk of bites and of pathogen transmission to humans. At the same time the uneven distribution of tick species might implicate in an unequal risk of tick-borne diseases within the same urban area.

Life cycle of the tick Amblyomma parvum Aragão, 1908 (Acari: Ixodidae) and suitability of domestic hosts under laboratory conditions.

Amblyomma parvum is a widespread Neotropical tick found on several domestic animals and is known to harbor a Rickettsia species of yet unknown pathogenicity. However its life cycle on, and suitability of, several of these hosts has not been described. In this work the biology of A. parvum is presented when fed on seven domestic hosts (chicken, dog, rabbit, horse, guinea pig, cattle and goat). The complete life cycle of the tick varied from 96.8 to 102 days. Highest engorgement weight of larvae was from ticks fed on horses and that of nymphs from guinea pigs. Highest larval yield was from guinea pigs and that of nymphs from horses. Engorged female and egg mass weights, yield and conversion of female weight to eggs rates were the highest in dog ticks and the lowest in goat ticks. The highest egg hatching rate was seen in ticks from dogs and the lowest in ticks from cattle. Overall it was seen that dogs were the best host for adult A. parvum ticks, and guinea pigs for immatures. Horses were also shown to be a good host for all tick stages. It can thus be affirmed that A. parvum is a host generalist tick, and its distribution is probably determined by environmental requirements rather than by hosts.

Ticks (Acari: Ixodidae) on dogs from Uberlândia, Minas Gerais, Brazil.

Uberlândia in Minas Gerais State, southeastern Brazil, has 622 000 inhabitants and is located in the Cerrado biome, the South American savannah. The city dog population is estimated at 82 000 and identification of tick species and infestation prevalence on this host has not been determined. A major infectious disease of dogs in the city, canine ehrlichiosis, is transmitted by Rhipicephalus sanguineus ticks. At the same time, autochthonous leishmaniosis has been recently described in the city and a role for dog ticks in the disease transmission has been supposed in Brazil. In this work, we present general information on dog ticks in Uberlândia municipality and region. Dogs from 33 farms and 31 districts were examined for ticks from July 2007 to February 2009. On the whole, 413 dogs were examined, 311 (75.3%) from the city and 102 (24.6%) from rural area. Overall infestation rate of dogs from Uberlândia was 37.3% and the mean infestation intensity was 3.25 parasites per dog. In the urban area, 100 dogs (32.2%) had ticks whereas 54 dogs (52.9%) from rural areas were infested. Four tick species were found: Rhipicephalus sanguineus, Amblyomma cajennense, Amblyomma ovale and Boophilus microplus. In the city, only R. sanguineus and one A. cajennense was found on dogs and R. sanguineus and A. ovale were the main dog ticks in rural areas.

Ecological aspects of the free-living ticks (Acari: Ixodidae) on animal trails within Atlantic rainforest in south-eastern Brazil.

In a recent ecological study of the ticks on animal trails within an area of Atlantic rainforest in south-eastern Brazil, Amblyomma aureolatum, A. brasiliense, A. incisum, A. ovale and Haemaphysalis juxtakochi were found questing on the vegetation. Most of the ticks recorded by a small, man-made dam on the forest border were A. dubitatum but a few A. brasiliense and A. cajennense, one A. incisum and one H. juxtakochi were also found. The seasonal activity of the ticks indicated that A. incisum and A. brasiliense had one generation/year. On the animal trails, most tick species and stages quested on the vegetation at a height of 30-40 cm above ground level. The questing larvae and adults of A. incisum tended to be found higher, however, with the greatest numbers recorded 40-50 cm (larvae) or 60-70 cm (adults) above ground level. Most of the adult ticks (81.1%-100%), nymphs (78.6%-100%) and larval clusters (100%) found on a forest trail remained questing at the same location over a 24-h period. Carbon-dioxide traps in the rainforest attracted <50% of the ticks observed questing on the nearby vegetation and, curiously, the CO2 traps set deep in the forest attracted far fewer ticks than similar traps set by the dam. The ecological relationships between the ticks, their hosts and the rainforest environment are discussed.

Eventos externos e internos da infecção de larvas e ninfas de Rhipicephalus sanguineus por Metarhizium anisopliae / External and internal events of Rhipicephalus sanguineus larvae and nymphs infection by Metarhizium anisopliae

Examinaram-se a adesão, a germinação, a penetração e a colonização de larvas e ninfas de Rhipicephalus sanguineus por Metarhizium anisopliae, assim como as lesões infringidas pelo fungo nas respectivas fases do ciclo de vida do ácaro. Realizaram-se infecções experimentais em 11 grupos contendo 250 larvas e 11 grupos contendo 75 ninfas de R. sanguineus, por meio de banho, durante três minutos sob agitação manual, em suspensão contendo 10(8) conídios/ml do fungo. Nos grupos-controles, o banho foi realizado usando o veículo da suspensão. Larvas e ninfas foram processadas para um estudo histopatológico e de microscopia eletrônica de varredura nos seguintes tempos após a infecção: uma e 18 horas, e um, dois, três, quatro, cinco, seis, sete, nove e 11 dias. A germinação dos conídios ocorreu em até 18 horas pós-inoculação, e o fungo penetrou nas larvas e ninfas através do tegumento, dois e três dias após a infecção, respectivamente. Após penetração, o fungo invadiu o corpo das larvas e ninfas, promovendo uma colonização difusa, sem preferência aparente por tecidos específicos. Lesões significativas não foram observadas. A morte das larvas e ninfas ocorreu no terceiro e quarto dias pós-infecção, e a esporulação do patógeno sobre o cadáver foi iniciada no sexto dia pós-infecção.

The adhesion, germination and colonization of Rhipicephalus sanguineus larvae and nymphs by Metarhizium anisopliae as well as the lesions caused by the fungus were studied. For this purpose, 11 groups of 250 larvae each and 11 groups of 75 nymphs each were bathed during 3 minutes under manual shaking in a 10(8) conidia/ml suspension. Corresponding control groups were bathed only in the suspension vehicle. Ticks were also submitted to both conventional microscopy and scanning eletronmicrocopy analyses at several post-infection periods (1 and 18 hours and 1, 2, 3, 4, 5, 6, 7, 9, and 11 days). Conidial germination occurred in less than 18 hours post-inoculation and the fungus penetration through the tegument into the larvae and nymphs in, respectively, two and three days post-infection. Following penetration, the fungus invaded the body of the ticks and colonized it diffusely without a noticeable predilection for tissue, but no apparent lesions were observed. Death of larvae and nymphs occurred on the 3rd and 4th post-infection days and pathogen sporulation over the dead tick began on the 6th post-infection day.

Distribution, hosts, 16S rDNA sequences and phylogenetic position of the Neotropical tick Amblyomma parvum (Acari: Ixodidae).

The hosts, distribution, intraspecific genetic variation and phylogenetic position of Amblyomma parvum (Acari: Ixodidae) have recently been re-assessed. Data on this tick's hosts and distribution were obtained not only from existing literature but also from unpublished records. Sequences of the ticks' mitochondrial 16S ribosomal DNA (rDNA) were used to evaluate genetic variation among specimens of A. parvum from different localities in Argentina and Brazil, and to explore the phylogenetic relationships between this tick and other Amblyomma species. Although several species of domestic and wild mammal act as hosts for adult A. parvum, most collected adults of this species have come from cattle and goats. Caviid rodents of the subfamily Caviinae appear to be the hosts for the immature stages. So far, A. parvum has been detected in 12 Neotropical biogeographical provinces (Chaco, Cerrado, Eastern Central America, Venezuelan Coast, Pantanal, Parana Forest, Caatinga, Chiapas, Venezuelan Llanos, Monte, Western Panamanian Isthmus, and Roraima) but the Chaco province has provided significantly more specimens than any other (P<0.0001). The 16S rDNA sequences showed just 0.0%-1.1% divergence among the Argentinean A. parvum investigated and no more than 0.2% divergence among the Brazilian specimens. The observed divergence between the Argentinean and Brazilian specimens was, however, greater (3.0%-3.7%). Although there is now molecular and morphological evidence to indicate that A. parvum, A. pseudoparvum, A. auricularium and A. pseudoconcolor are members of a natural group, previous subgeneric classifications do not reflect this grouping. The subgeneric status of these tick species therefore needs to be re-evaluated. The 16S-rDNA-based evaluation of divergence indicates that the gene flow between Argentinean and Brazilian 'A. parvum' is very limited and that the Argentinean 'A. parvum' may be a different species to the Brazilian.

Renal dysplasia in a Limousin calf

Descreve-se um caso de displasia renal em um bezerro Limousin, macho, de quatro meses. O animal apresentava perda de peso, baixa taxa de crescimento, anorexia, apatia, diarréia escura fétida e uremia, sem melhora apesar de tratamento. O bezerro foi sacrificado para interromper o sofrimento adicional e submetido à necropsia. Ao exame foi observado que os rins estavam pequenos, firmes, pálidos e com superfície rugosa. A cápsula estava aderida à uma superfície subcapsular irregular. O córtex tinha aparência difusamente pálida e fibrosa e apresentava múltiplos focos brancos de fibrose. A junção córtico-medular estava indistinta. O exame histologico dos rins revelou múltiplos glomérulos imaturos com núcleo periférico, capilares inaparentes e padrão arbóreo. O córtex renal apresentou túbulos primitivos com epitélio cubóide ou cilíndrico envolvido por mesênquima corado somente pelo alcian blue e não pelo tricrômico de Masson. Foi também observada leve fibrose intersticial na medula renal. Os rins mostravam estruturas em estágio inapropriado de desenvolvimento ou anômalas.

Copper toxicosis in sheep fed dairy cattle ration in São Paulo, Brazil

Intoxicação crônica por cobre foi observada em um rebanho de 20 ovinos no município de Franca, São Paulo. Três meses após o início do arraçoamento com feno e ração concentrada peletizada para bovinos de leite, seis animais apresentaram anorexia, icterícia severa e urina marrom escura, e vieram a óbito. Diagnosticou-se doença hemolítica com base em sinais clínicos, alterações macroscópicas observadas na necropsia e observações histológicas. A necropsia todos os ovinos apresentaram icterícia severa, fígado amarelado com padrão lobular evidente e rins escuros. As principais alterações histológicas incluíram necrose hepática periacinar e nefrose hemoglobinúrica. Acúmulos de cobre foram demonstrados nos hepatócitos e macrófagos pela coloração rodamina e níveis elevados de cobre mediante espectrofotometria de absorção atômica no soro, fígado e rins de dois ovinos afetados e na ração fornecida.

Ticks (Ixodidae) on humans in South America.

Twenty eight species of Ixodidae have been found on man in South America (21 Amblyomma, 1 Boophilus, 2 Dermacentor, 2 Haemaphysalis, 1 Ixodes and 1 Rhipicephalus species). Most of them are rarely found on man. However, three species frequently parasitize humans in restricted areas of Argentina (A. neumanni reported from 46 localities), Uruguay (A. triste from 21 sites) and Argentina-Brazil (A. parvum from 27 localities). The most widespread ticks are A. cajennense (134 localities in Argentina, Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Paraguay, Suriname and Venezuela), A. ovale (37 localities in Argentina, Brazil, Ecuador, French Guiana, Guyana, Paraguay, Suriname and Venezuela) and A. oblongoguttatum (28 sites in Brazil, Colombia, French Guiana, Guyana, Suriname and Venezuela). Amblyomma aureolatum (18 localities in Argentina, Brazil, French Guiana and Paraguay), A. cajennense, and A. triste are vectors of rickettsioses to man in South America. A better understanding of the respective roles of these and other tick species in transmitting pathogens to humans will require further local investigations. Amblyomma ticks should be the main subjects of these studies followed by species of Boophilus, Dermacentor, Haemaphysalis and Rhipicephalus species. In contrast with North America, Europe and Asia, ticks of the genus Ixodes do not appear to be major players in transmitting diseases to human. Indeed, there is only one record of an Ixodes collected while feeding on man for all South America.

Microscopic features of tick-bite lesions in anteaters and armadillos: Emas National Park and the Pantanal region of Brazil.

The naturally occurring wildlife host associations between ticks and tick-borne pathogens found in the neotropics are poorly described. Understanding tick-bite lesions is important as these are the site of host reaction to and pathogen delivery by ticks. As part of a comprehensive study concerning established and emerging tick-host relationships. the present work describes some aspects of tick-bite lesions in anteaters and armadillos captured at the Emas National Park and the Pantanal region of Brazil. Biopsies were of skin were taken and examine. Tick feeding sites of all animals displayed an eosinophilic homogeneous mass, the cement cone, and, occasionally, a feeding cavity underneath the tick attachment site. At these locations the epidermis was usually thickened due to keratinocyte hyperplasia. The main dermal changes included tissue infiltration with a varying number of inflammatory cells, edema, hemorrhage. and vascular dilatation. Cellular infiltration of the dermis was predominantly composed of mononuclear cells, neutrophils. and eosinophils. Mast cells were also seen in both non-parasitized and parasitized skin but were found in higher numbers at perivascular sites and in parasitized skin. Basophils were not seen at tick attachment sites of anteaters or armadillos.

Hypersensitivity induced in dogs by nymphal extract of Amblyomma cajennense ticks (Acari:Ixodidae).

In general, hosts develop resistance to ticks after repeated infestations; nevertheless, several studies on naturally occurring host-tick interactions were unable to detect resistance of hosts to ticks even after repeated infestations. The purpose of this investigation was to study the type of cutaneous hypersensitivity to unfed nymphal extract of A. cajennense in dogs, which, unlike guinea pigs, do not develop resistance. A first, but no second, peak in skin reaction was observed, suggesting that cellular immunity is an important mechanism of resistance to ticks. This may partially explain why guinea pigs, but not dogs, develop resistance against ticks.

Development of resistance to nymphs of Amblyomma cajennense ticks (Acari:Ixodidae) in dogs.

Ticks have long been regarded as constraints to humans and domestic animals, but hosts often develop resistance to ticks after repeated infestations. The purpose of this investigation was to study the possible acquisition of immunity in domestic dogs to nymphs of A. cajennense by determining the tick alimentary performance after successive controlled infestations. Mean engorged weight of nymphs was not significantly different among the three infestations; molting rate from nymph to adult ticks, and the percentage of nymph recovery were also very close in all infestations. These results are similar to those obtained in studies of the dog-adult Rhipicephalus sanguineus interface. It is concluded that domestic dogs do not develop resistance against nymphs of A. cajennense ticks.