Seroprevalence of Rickettsia typhi and Rickettsia conorii infection among rodents and dogs in Egypt

A serological survey of 1813 rodent and 549 dog sera, collected from 1979 to 1986 from animals in 16 Egyptian Governorates were tested for antibody to Rickettsia typhi and Rickettsia conorii by the indirect fluorescent antibody test. Only three of 82 (4%) sera from Rattus rattus collected near Aswan had antibody to R. conorii. The prevalence of R. typhi antibody in dog sera was only 0.4% (n = 549) while 25% (n = 547) of Rattus norvegicus and 11% (n = 1138) of R. rattus had measurable antibodies. Among the other rodents, antibody was demonstrated in only 2% (n = 45) of Arvicanthis spp., and 1% (n = 83) of Acomys spp. Collectively, rodents captured in the Nile Delta had a higher prevalence (mean 24% (n = 787] than those captured in the Nile Valley (mean 4% (n = 650]. Antibody to R. typhi was detected in rodents collected in all port cities: ismailiya, 13%; Port Said, 9%; Suez, 9%; Safaga, 16%; Quseir, 32% and Alexandria, 34%. These data showed evidence of R. typhi infection among rodents in widespread geographic localities of Egypt and suggested that infected rodents may be a source of human infections.     

Experimental infection of dogs with a Zimbabwean strain of Rickettsia conorii.

Seroconversion was demonstrated in dogs artificially infected with a Zimbabwean strain of Rickettsia conorii. No haematological or biochemical abnormalities were found and the only clinical signs observed were pain, erythema and oedema at the inoculation site and regional lymphadenopathy. Intermittent rickettsaemia was detected using the centrifugation shell vial technique up to 10 days post inoculation.     

Experimentally infected human body lice (pediculus humanus humanus) as vectors of Rickettsia rickettsii and Rickettsia conorii in a rabbit model

The human body louse, the natural vector of Rickettsia prowazekii, is able to experimentally transmit the normally flea-borne rickettsia R. typhi, suggesting that the relationships between the body louse and rickettsiae are not specific. We used our experimental infection model to test the ability of body lice to transmit two prevalent tick-borne rickettsiae. Each of two rabbits was made bacteremic by injecting intravenously 2 x 10(6) plaque-forming units of either R. rickettsii or R. conorii. Four hundred body lice were infected by feeding on the bacteremic rabbit and were compared with 400 uninfected lice. Each louse group was fed once a day on a separate seronegative rabbit. The survival of infected lice was not different from that of uninfected controls. Lice remained infected for their lifespan, excreted R. rickettsii and R. conorii in their feces, but did not transmit the infection to their progeny. The nurse rabbit of uninfected lice remained asymptomatic and seronegative. Those rabbits used to feed infected lice developed bacteremia and seroconverted. Although the body louse is not a known vector of spotted fevers, it was able in our study to acquire, maintain, and transmit both R. rickettsii and R. conorii.     

Rickettsia conorii in humans and dogs: a seroepidemiologic survey of two rural villages in Israel

The prevalence of IgG-antibodies reactive with an Israeli strain of Rickettsia conorii (Israeli strain 487), the agent of Israeli spotted fever, was examined in humans and dogs from two rural villages in Israel where the disease has been reported in humans. Sixty-nine of 85 (81%) canine sera and 14 of 136 (10%) of human sera had anti-R. conorii antibodies. No direct association could be made between seropositivity of people and ownership of a seropositive dog. This study indicates that exposure to spotted fever group rickettsiae was highly prevalent among dogs compared with humans in the two villages examined, probably reflecting a greater exposure rate of canines to the tick vector. These results support a previous suggestion that canine serology could be a sensitive indicator for the presence and magnitude of human exposure to R. conorii.     

Molecular and morphological comparison of hookworms from genus Uncinaria invading red fox (Vulpes vulpes) and dog (Canis familiaris)

Two species of hookworms from genus Uncinaria have been found so far in Poland. Uncinaria stenocephala infects mainly dog, wolf and red fox, whereas Uncinaria criniformis is a parasite of mustelids (but it was also reported from red fox). 19 male and 29 female hookworms from red foxes have been compared with 10 male and 12 female worms from dogs. Hookworms from dogs were generally smaller than these from foxes, but no other morphological differences could be found. These hookworms were qualified to species Uncinaria stenocephala on the ground of morphology of male. Genomic DNA samples have been isolated from these hookworms and segments of rDNA including part of small subunit of ribosomal RNA gene; internal transcribed spacer 1 (ITS1); 5.8 S ribosomal RNA; internal transcribed spacer 2 (ITS2) and part of large subunit of ribosomal RNA have been amplified and sequenced. Sequences from Uncinaria obtained both from foxes and dogs have shown very high similarity to the sequence of Uncinaria stenocephala, so all examined hookworms have been classified as belonging to this species.     

Molecular evidence supports the role of dogs as potential reservoirs for Rickettsia felis

Rickettsia felis causes flea-borne spotted fever in humans worldwide. The cat flea, Ctenocephalides felis, serves as vector and reservoir host for this disease agent. To determine the role of dogs as potential reservoir hosts for spotted fever group rickettsiae, we screened blood from 100 pound dogs in Southeast Queensland by using a highly sensitive genus-specific PCR. Nine of the pound dogs were positive for rickettsial DNA and subsequent molecular sequencing confirmed amplification of R. felis. A high prevalence of R. felis in dogs in our study suggests that dogs may act as an important reservoir host for R. felis and as a potential source of human rickettsial infection.     

Host- and microbe-related risk factors for and pathophysiology of fatal Rickettsia conorii infection in Portuguese patients

BACKGROUND: The pathophysiologic mechanisms that determine the severity of Mediterranean spotted fever (MSF) and the host-related and microbe-related risk factors for a fatal outcome are incompletely understood. METHODS: This prospective study used univariate and multivariate analyses to determine the risk factors for a fatal outcome for 140 patients with Rickettsia conorii infection admitted to 13 Portuguese hospitals during 1994-2006 with documented identification of the rickettsial strain causing their infection. RESULTS: A total of 71 patients (51%) were infected with the Malish strain of Rickettsia conorii, and 69 (49%) were infected with the Israeli spotted fever (ISF) strain. Patients were admitted to the intensive care unit (40 [29%]), hospitalized as routine inpatients (95[67%]), or managed as outpatients (5[4%]). Death occurred in 29 adults (21%). A fatal outcome was significantly more likely for patients infected with the ISF strain, and alcoholism was a risk factor. The pathophysiology of a fatal outcome involved significantly greater incidence of petechial rash, gastrointestinal symptoms, obtundation and/or confusion, dehydration, tachypnea, hepatomegaly, leukocytosis, coagulopathy, azotemia, hyperbilirubinemia, and elevated levels of hepatic enzymes and creatine kinase. Some, but not all, of these findings were observed more often in ISF strain-infected patients. CONCLUSIONS: Although fatalities and similar clinical manifestations occurred among both groups of patients, the ISF strain was more virulent than the Malish strain. Multivariate analysis revealed that acute renal failure and hyperbilirubinemia were most strongly associated with a fatal outcome.     

Serological reactivity to Ehrlichia canis, Anaplasma phagocytophilum, Neorickettsia risticii, Borrelia burgdorferi and Rickettsia conorii in dogs from northwestern Spain

The aim of the present work was to investigate the seroprevalence against Ehrlichia canis (Ec), Anaplasma phagocytophilum (Ap), Neorickettsia risticii (Nr), Rickettsia conorii (Rc), and Borrelia burgdorferi (Bb) in two different clusters of canine samples from Northwestern Spain. Cluster 1 included 479 dogs presented at veterinary clinics located in Ourense and Pontevedra. Cluster II included 170 dogs from the public kennel of Ourense. All 649 canine serum samples were analyzed by immunofluorescent antibody test. Prevalences against the above-mentioned agents in cluster I were: Rc (24.6%), Bb (6.26%), Ec (3.13%), Ap (5.01%), and Nr (1.04%), whereas for cluster II were: Rc (50%), Bb (8.8%), Ec (54.7%), Ap (45.3%), and Nr (4.7%). Rc was significantly associated with age and history of exposure to ticks, and Bb showed a statistical relationship with age and clinical status. Ec and Ap were related to the occupation of the dogs, with stray dogs being the most frequently seropositive. Furthermore, seroreactivity against Ec and Ap was significantly higher in Ourense than in Pontevedra. The univariate analysis demonstrated a significant concomitant seroreactivity between Ec and Ap and between Rc and Ec and Ap antigens. The seroreactivity to Nr must be interpreted very cautiously as this infectious agent has been seldom reported outside North America.     

Capacity of European animals as reservoir hosts for the Lyme disease spirochete.

The abundance of spirochete-infected Ixodes ricinus ticks naturally derived from endemic rodents was compared to identify the reservoir hosts of the agent of Lyme disease at a series of enzootic sites in Central Europe. Black-striped mice appear to be the most important rodent host for the tick and infect more ticks with Borrelia burgdorferi than do other mice and voles tested. Although rodents infect about half of the ticks that feed on them, lizards infect none. These spirochete-incompetent hosts dilute the force of transmission because many nymphal ticks feed on them. Older male hosts are more heavily infested by subadult ticks than are younger or female hosts. The intensity of transmission of the agent of Lyme disease at particular Central European sites appears to correlate directly with the presence of black-striped mice and inversely with that of lizards.     

Immunological inquiry for the epidemiology of leptospirosis in Canis familiaris in Salvador, Bahia, Brazil

A total of 430 dogs were immunologically examined in Salvador, Bahia, Brazil, and 21.6% of them were positive. The animals were selected through an aleatory pattern, according to the division of the City in 18 residential zones a division which had been established by the vaccination campaign against canis hydrophobia. The serotypes icterohemorrhagiae and canicola were the most frequently registered. Between the sexes, the male presented the highest index of positivity, though the difference wasn't statistically significant. The period of age ranging from 12 to 48 months comprised 67.7% of the investigations. Mestizo dogs presented a higher frequency of positivity than any other race and the areas of Nordeste de Amaralina, Liberdade and Quintas showed the greatest percentages of positive dogs.     

Sequences of islet amyloid polypeptide precursors of an old world monkey,the pig-tailed macaque (Macaca nemestrina), and the dog (Canis familiaris)

Summary The 37-amino acid islet amyloid polypeptide represents the major protein component present in islet amyloid deposits. Although the presence of islet amyloid is a characteristic pathological feature of the islets of humans, monkeys and cats with Type 2 (non-insulin-dependent) diabetes mellitus, it is not found in the islets of diabetic rats, mice or dogs. To further explore the molecular basis for these species differences in amyloid deposition we have used a polymerase chain reaction based method to clone cDNAs encoding the monkey (Macaca nemestrina) and dog (Canis familiaris) islet amyloid polypeptide precursors. The predicted amino acid sequence of the monkey precursor is 96% identical to that of the human protein; differences include one replacement in the signal peptide and three in the islet amyloid polypeptide domain. The sequence of the dog precursor is most closely related to that of the cat protein (85% identity); the sequences of dog and cat islet amyloid polypeptide differ only at two positions and are identical in the region of amino acids 20–29, the region thought to be primarily responsible for amyloidogenesis. Thus, amino acid residues in addition to those at positions 20–29 may facilitate the aggregation of islet amyloid polypeptide. The presence of amyloid deposits in some dog pancreatic endocrine tumours suggests that the dog protein can be amyloidogenic, perhaps due to elevated expression of islet amyloid polypeptide by the tumours relative to normal islets.     

House flies (Musca domestica) as transport hosts of Cryptosporidium parvum.

Refuse and promiscuous-landing synanthropic filth flies, such as house flies (Musca domestica), are recognized as transport hosts for a variety of protozoan and metazoan parasites in addition to viral and bacterial pathogens of public health importance. Exposure of adult M. domestica to 20 ml of bovine diarrheal feces containing Cryptosporidium parvum oocysts (2.0 x 10(5) oocysts/ml) resulted in intense deposition of the oocysts through fly feces on the surfaces visited by the flies (mean = 108 oocysts/cm2). Cryptosporidium parvum oocysts were detected by immunofluorescent antibodies on the exoskeleton of adult flies and in their digestive tracts. An average of 267, 131, 32, 19, and 14 oocysts per adult fly were eluted from its exoskeleton on days 3, 5, 7, 9, and 11 after they emerged, respectively. Approximately 320 C. parvum oocysts per pupa were eluted from the external surface of the pupae derived from maggots that breed in a substrate contaminated with the bovine feces; the oocysts were numerous on maggots (approximately 150 oocysts/maggot). Adult and larval stages of house flies breeding or having access to C. parvum-contaminated substrate will mechanically carry the oocysts in their digestive tracts and on their external surfaces.     

Identification of a Novel Uncultured Rickettsia Species Strain (Rickettsia Species Strain Tselenti) in Cyprus

In a previous study conducted in Cyprus, various spotted fever group Rickettsia species were detected and identified in ticks by molecular analysis. Among them, a partially characterized Rickettsia species was detected in Hyalomma anatolicum excavatum and Rhipicephalus turanicus ticks. We report characterization of this rickettsial strain by using polymerase chain reaction sequencing analysis of partial citrate synthase A, outer membrane protein A, outer membrane protein B, and 17-kD protein genes. We propose a provisional name Rickettsia sp. strain Tselenti for this strain until it is isolated and further characterized.     

Experimental and field studies on the suitability of raccoons (Procyon lotor) as hosts for tick-borne pathogens

We investigated the experimental susceptibility and natural exposure of raccoons (Procyon lotor) to five tick-borne pathogens of human and veterinary importance, Ehrlichia canis, E. chaffeensis, E. ewingii, Anaplasma phagocytophilum (ApVariant 1 and Ap-ha HGE-1 strains), and Borrelia lonestari. Infections were assessed by polymerase chain reaction (PCR), indirect fluorescent antibody (IFA) testing, and/or culture isolation methods for at least 30 days postinoculation (DPI). Two E. chaffeensis-inoculated raccoons seroconverted and were transiently PCR positive. One raccoon was culture positive. Laboratory raised Amblyomma americanum nymphs fed on a third infected raccoon failed to become infected. Two A. phagocytophilum (HGE-1)-inoculated raccoons became PCR positive and seroconverted. Both remained positive for at least 74 DPI. In contrast, raccoons inoculated with A. phagocytophilum (Ap-Variant 1) were only transiently PCR positive and only seroconverted with low titers. No evidence of infection was observed for E. ewingii- and B. lonestari-inoculated raccoons. Only one E. canis-inoculated raccoon was PCR positive 3 DPI. Serologic testing of wild raccoons from five populations (3 infested with ticks) in Georgia and Florida showed antibodies reactive with E. chaffeensis in the 3 tick-infested populations (range of 30%-46%), E. canis in the same three populations (8%-23%), A. phagocytophilum in a single raccoon from Florida (12%), and Borrelia spp. in all 5 populations (8%-53%). All raccoons were PCR negative for tick-borne pathogens. These data suggest that raccoons are likely not important reservoirs of E. canis, E. ewingii, or B. lonestari. However, raccoons are experimentally susceptible and naturally exposed to E. chaffeensis, and these data support the previous finding that raccoons may be involved in the natural history of A. phagocytophilum.     

Blood-meal analysis for the identification of reservoir hosts of tick-borne pathogens in Ireland

The results of analysis of blood-meal remnants in unfed nymphs, despite relatively low detection levels (49.4%, n = 322), support the conclusion from an earlier study that small rodents are relatively unimportant as reservoir hosts of B. burgdorferi s.l. in this particular area, and suggest that songbirds (Passeriformes) are the most significant hosts in this respect. Tick (Ixodes ricinus) abundance was greater in the present study, but the overall Borrelia burgdorferi s.l.-infection prevalence of nymphal ticks was the same (12.2%), and the relative proportions of the various Borrelia burgdorferi s.l. genospecies were similar. B. garinii and B. valaisiana were the most frequent, B. burgdorferi s.s the least frequent, and B. afzelii of intermediate frequency. An unusually high proportion of nymphs (39%) with multiple infections of different B. burgdorferi genospecies was detected, and Borrelia spp. related to relapsing-fever spirochetes were detected in Ireland for the first time. The results of the present study contribute to the validation of blood-meal analysis as a means of determining the host origin of certain pathogens in unfed questing ticks, and raise some questions concerning the extent of B. burgdorferi s.l. host specificity.     

Pteropid bats are confirmed as the reservoir hosts of henipaviruses: a comprehensive experimental study of virus transmission

Bats of the genus Pteropus have been identified as the reservoir hosts for the henipaviruses Hendra virus (HeV) and Nipah virus (NiV). The aim of these studies was to assess likely mechanisms for henipaviruses transmission from bats. In a series of experiments, Pteropus bats from Malaysia and Australia were inoculated with NiV and HeV, respectively, by natural routes of infection. Despite an intensive sampling strategy, no NiV was recovered from the Malaysian bats and HeV was reisolated from only one Australian bat; no disease was seen. These experiments suggest that opportunities for henipavirus transmission may be limited; therefore, the probability of a spillover event is low. For spillover to occur, a range of conditions and events must coincide. An alternate assessment framework is required if we are to fully understand how this reservoir host maintains and transmits not only these but all viruses with which it has been associated.     

Red fox (Vulpes vulpes) as reservoir of parasites and source of zoonosis

Red fox (Vulpes vulpes) as reservoir of parasites and source of zoonosis. This review presents data from Europe and Poland on the prevalence of helminth and protozoan parasites in red foxes (Vulpes vulpes). The most common nematodes were geohelminths: Uncinaria stenocephala, Toxocara canis and Toxocara leonina. As concerning Trichinella genus T. britovi was found more often than T. spiralis. Among tapeworms the following species were recorded: Mesocestoides lineatus, Taenia sp., and Echinococcus multilocularis. Detected cases of E. multilocularis together with an increase of fox population during last few years create a potential human risk of infection. The results of many studies indicate rare presence of trematodes (Alaria alata) and protozoan parasites (Toxoplasma gondii, Neospora caninum, Leishmania spp., Eimeria spp.) in red foxes.     

Evolution in coyotes (Canis latrans) in response to the megafaunal extinctions

Living coyotes modify their behavior in the presence of larger carnivores, such as wolves. However, little is known about the effects of competitor presence or absence on morphological change in coyotes or wolves over long periods of time. We examined the evolution of coyotes and wolves through time from the late Pleistocene, during which many large carnivorous species coexisted as predators and competitors, to the Recent; this allowed us to investigate evolutionary changes in these species in response to climate change and megafaunal extinctions at the end of the Pleistocene. We measured postcranial skeletal morphologies of wolves (Canis lupus) and coyotes (C. latrans) from Pleistocene-aged tar deposits, as well as early, mid, and recent Holocene populations of both. We found few morphological differences between Pleistocene and Holocene wolf populations. Conversely, we found many differences in coyotes: Pleistocene coyotes were larger and more robust than Holocene populations. However, within 1,000 y of the megafaunal extinctions, coyotes are morphologically indistinguishable from modern populations. We cannot attribute these differences directly to climate change because modern coyotes do not follow Bergmann's rule, which states body size increases with decreasing temperature. Instead, we suggest that Pleistocene coyotes may have been larger and more robust in response to larger competitors and a larger-bodied prey base. Although we cannot separate competition from predator-prey interactions, this study indicates that the effects of biotic interactions can be detected in the fossil record.