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PubMed1986

Biology of Arboledas virus, a new phlebotomus fever serogroup virus (Bunyaviridae: Phlebovirus) isolated from sand flies in Colombia.

Six isolates of a new phlebotomus fever serogroup virus, designated Arboledas virus, were obtained from sand flies (Lutzomyia spp.) collected in northeastern Colombia. One of the isolates was made from a pool of male sand flies. By immunofluorescence, Arboledas virus is related to Caimito and Pacui viruses; by neutralization test, it is distinct. Arboledas virus neutralizing antibodies were found in the sera of opossums (Didelphis marsupialis) and humans living in the study area. D. marsupialis inoculated with the virus developed a viremia of four days' duration, and sand flies (Lutzomyia gomezi) feeding on a viremic opossum were readily infected. Transovarial transmission of Arboledas virus was also demonstrated in experimentally infected Lu. gomezi. Results of the above laboratory studies suggest that Arboledas virus is maintained in nature by two mechanisms: vertical (transovarial) transmission in the insect vector, and an alternating marsupial-sand fly cycle. The implications of this complex maintenance cycle for other phleboviruses are discussed.

Animals↗
PubMed1989

International spread of disease by air travel.

Rapid air travel has increased the potential for international transmission of infectious diseases. Important aspects of this problem include the transmission of foodborne and waterborne illnesses, the translocation of insect vectors, the rapid transport of individuals with incubating illnesses, the direct transmission of diseases inside aircraft and the transmission of zoonoses through animal transport. Infectious outbreaks on aircraft and in the vicinity of airports have included influenza, staphylococcal gastroenteritis, salmonellosis, cholera and malaria.

Aircraft↗
PubMed1988

Filariasis in the Igwun River Basin, Nigeria: an epidemiological and clinical study with a note on the vectors.

In a cross-sectional, epidemiological and parasitological study of human filariasis, 845 individuals were examined in settlements along the Igwun Basin, Imo State, Nigeria. Four different filarial nematode species were identified. Two hundred and fifty-six (30.3%) of the individuals examined were positive for Onchocerca volvulus, 113 (13.4%) for Mansonella perstans, 76 (9.6%) for Wuchereria bancrofti and 77 (9.1%) for Loa loa. Microfilarial rates increased with age of individuals and showed a tendency towards higher prevalence rates in males than in females. The intensity of O. volvulus infection was high, with the highest microfilarial density of 44 mf mg-1 snip which occurred in the 40-49-year-old individuals. In W. bancrofti and L. loa infections, infections of over 1000 mf 20 ml-1 blood were recorded in 15.8% and 19.5% of individuals, respectively. Observed clinical signs were associated with inflammatory, lympho-obstructive and ocular manifestations. In M. perstans infections all clinical cases were inflammatory. In W. bancrofti, 44.4% of clinical cases were inflammatory, and lympho-obstructive manifestations consisted of 23.8% chyluria, 12.7% hydrocele and 19.1% elephantiasis. In L. loa infections all clinical cases were inflammatory with indications of Calabar swellings. In O. volvulus infections 23.5% of clinical cases were inflammatory, while 76.5% showed ocular manifestations. The absence of blindness despite high O. volvulus infection rates was remarkable. The presence of potential insect vectors and the occurrence of clinical signs are indications of active transmissions.

Adolescent↗
PubMed2003

Identification and mapping of the promoter for the gene encoding the ferritin heavy-chain homologue of the yellow fever mosquito Aedes aegypti.

Mosquitoes are responsible for the transmission of numerous human diseases. The recent development of transgenic mosquitoes provides a new tool to examine molecular interactions between insect vectors and the pathogens they transmit. One focus in generating transgenic mosquito lies on expressing anti-pathogenic proteins at primary sites of pathogenic invasions, specifically the mosquito gut. Promoters that direct the expression of anti-pathogenic proteins in the mosquito gut are thus sought after because they may provide ways to hinder pathogenic development in the mosquito. Here, we report the identification and mapping of a strong promoter from the Aedes aegypti ferritin heavy-chain homologue (HCH) gene. All known insect ferritin HCH genes are expressed in the gut and inducible by an iron overload. Our transfection assays and DNase I footprinting analyses show that the mosquito ferritin HCH-gene contains regulatory elements both upstream and downstream of the transcriptional start site. The promoter of this gene contains a CF2 site, two GATA-binding sites, an E2F site, a TATA-box, an AP-1 site and a C/EBP binding site.

Aedes↗
PubMed2000

Mosquito immune responses and malaria transmission: lessons from insect model systems and implications for vertebrate innate immunity and vaccine development.

The introduction of novel biochemical, genetic, molecular and cell biology tools to the study of insect immunity has generated an information explosion in recent years. Due to the biodiversity of insects, complementary model systems have been developed. The conceptual framework built based on these systems is used to discuss our current understanding of mosquito immune responses and their implications for malaria transmission. The areas of insect and vertebrate innate immunity are merging as new information confirms the remarkable extent of the evolutionary conservation, at a molecular level, in the signaling pathways mediating these responses in such distant species. Our current understanding of the molecular language that allows the vertebrate innate immune system to identify parasites, such as malaria, and direct the acquired immune system to mount a protective immune response is very limited. Insect vectors of parasitic diseases, such as mosquitoes, could represent excellent models to understand the molecular responses of epithelial cells to parasite invasion. This information could broaden our understanding of vertebrate responses to parasitic infection and could have extensive implications for anti-malarial vaccine development.

Animals↗
PubMed2000

Amplification of a specific repetitive DNA sequence for Trypanosoma rangeli identification and its potential application in epidemiological investigations.

Trypanosoma rangeli can infect humans as well as the same domestic and wild animals and triatomine vectors infected by Trypanosoma cruzi in Central and South America. This overlapping distribution complicates the epidemiology of American trypanosomiasis due to the cross-reactivity between T. rangeli and T. cruzi antigens and the presence of conserved DNA sequences in these parasites. We have isolated a T. rangeli-specific DNA repetitive element which is represented in approximately 103 copies per parasite genome and is distributed in several chromosomal bands. The 542-bp nucleotide sequence of this element, named P542, was determined and a PCR assay was standardized for its amplification. The sensitivity of the assay is high, allowing the detection of one tenth of the DNA content of a single parasite. The presence of the P542 element was confirmed in 11 T. rangeli isolates from mammalian hosts and insect vectors originating from several countries in Latin America. Negative amplification was observed with different T. cruzi strains and other trypanosomatids. The potential field application of the P542 PCR assay was investigated in simulated samples containing T. rangeli and/or T. cruzi and intestinal tract and feces of Rhodnius prolixus. Epidemiological studies were conducted in DNA preparations obtained from the digestive tracts of 12 Rhodnius colombiensis insects collected in a sylvatic area in Colombia. Positive amplification of the P542 element was obtained in 9/12 insects. We have also compared in the same samples the diagnostic performance of two PCR assays for the amplification of the variable domain of minicircle kinetoplast DNA (kDNA) and of the large subunit (LSU) of the ribosomal RNA gene of T. cruzi and T. rangeli. Data indicate that the kDNA PCR assay does not allow diagnosis of mixed infections in most insects. On the other hand, the PCR assay of the LSU RNA gene showed lower sensitivity in the detection of T. rangeli than the PCR assay of the P542 element. It is predicted that the use of sensitive detection techniques will indicate that the actual distribution of T. rangeli in America is wider than presumed.

Animals↗
PubMed2000

Phylogenetic relationships of bluetongue viruses based on gene S7.

Previous phylogenetic analyses based on bluetongue virus (BTV) gene segment L3, which encodes the inner core protein, VP3, indicated a geographical distribution of different genotypes. The inner core protein, VP7, of BTV has been identified as a viral attachment protein for insect cell infection. Because the inner core proteins are involved with infectivity of insect cells, we hypothesized that certain VP7 protein sequences are preferred by the insect vector species present in specific geographic locations. We compared the gene segment S7, which encodes VP7, from 39 strains of BTV isolated from Central America, the Caribbean Basin, the United States, South Africa and Australia. For comparison, the S7 sequences from strains of the related orbiviruses, epizootic hemorrhagic disease virus (EHDV) and African horse sickness virus (AHSV) were included. The S7 gene was highly conserved among BTV strains and fairly conserved among the other orbiviruses examined. VP7 sequence alignment suggests that the BTV receptor-binding site in the insect is also conserved. Phylogenetic analyses revealed that the BTV S7 nucleotide sequences do not unequivocally display geographic distribution. The BTV strains can be separated into five clades based on the deduced VP7 amino acid sequence alignment and phylogeny but evidence for preferential selection by available gnat species for a particular VP7 clade is inconclusive. Differences between clades indicate allowable variation of the VP7 binding protein.

Amino Acid Sequence↗
PubMed2002

Molecular epidemiology of cutaneous leishmaniasis in Venezuela.

This paper discusses the utility of a set of primers (3J1, 3J2) designed from a repetitive nuclear deoxyribonucleic acid sequence for the diagnosis of Leishmania braziliensis infection in samples obtained from humans, insect vectors and mammalian reservoir hosts from different endemic areas in Venezuela. A high incidence of Leishmania (Viannia) braziliensis infection was found in the endemic areas studied. The sensitivity and specificity of the primers used were adequate for the identification of the natural vectors and reservoir hosts of L. (V.) braziliensis. The polymerase chain reaction was more sensitive than culture and stained smear examination in the diagnosis of cutaneous leishmaniasis, detecting 80% of cases compared to 42% and 72%, respectively.

Animals↗
PubMed2005

Potential impacts of climate change on infectious diseases in the Arctic.

Climate change could cause changes in the incidence of infectious diseases in Arctic regions. Higher ambient temperatures in the Arctic may result in an increase in some temperature sensitive foodborne diseases such as gastroenteritis, paralytic shellfish poisoning and botulism. An increase in mean temperature may also influence the incidence of infectious diseases of animals that are spread to humans (zoonoses) by changing the population and range of animal hosts and insect vectors. An increase in flooding events may result in outbreaks of waterborne infection, such as Giardia lamblia or Cryptospordium parvum. A change in rodent and fox populations may result in an increase in rabies or echinococcosis. Temperature and humidity influence the distribution and density of many arthropod vectors which in turn may influence the incidence and northern range of vectorborne diseases such as West Nile virus. Recommendations include: the strenghtening of public health systems, disease surveillance coordinated with climate monitoring, and research into the detection, prevention, control and treatment of temperature-sensitive infectious diseases.

Animals↗
PubMed2003

Leishmania tropica in the black rat (Rattus rattus): persistence and transmission from asymptomatic host to sand fly vector Phlebotomus sergenti.

Black rats (Rattus rattus) receiving Leishmania tropica injected intradermally into the ear were studied for the persistence of parasites and infectivity to natural sand fly vector. The mammalian host, the parasite, and the vector all originated from the endemic focus of Urfa, Turkey. Rats did not develop lesions or any apparent signs of disease, although at the site of inoculation they harboured live parasites capable of infecting sand flies. The number of L. tropica amastigotes detected in the inoculated ear by quantitative real-time PCR ranged from 5 x 10(3) to 10(6). Parasite DNA was also present in the tail and contralateral ear, sites distant from inoculation. After feeding on the ears of asymptomatic rats, Phlebotomus sergenti became infected with L. tropica. The average infection rate was 2.9%, and rats were infective for sand flies even 24 months post infection. The infectivity of the vertebrate host for insect vector was therefore not linked to the symptomatic stage of the infection. Such lack of correlation between clinical symptoms and infectivity to sand flies was reported previously for Leishmania infantum, the agent of visceral leishmaniasis; for species causing cutaneous leishmaniasis, however, this is the first evidence of transmission from a host without any visible cutaneous changes. If confirmed in the field, transmission from the asymptomatic host would be of great epidemiological significance.

Animals↗
PubMed2006

Phylogenetic analysis of Buggy Creek virus: evidence for multiple clades in the Western Great Plains, United States of America.

We present the first detailed phylogenetic analysis of Buggy Creek virus (BCRV), a poorly known alphavirus with transmission cycles involving a cimicid swallow bug (Oeciacus vicarius) vector and cliff swallows (Petrochelidon pyrrhonota) and house sparrows (Passer domesticus) as the principal avian hosts. Nucleotide sequences of a 2,075-bp viral envelope glycoprotein-coding region, covering the entire PE2 gene, were determined for 33 BCRV isolates taken from swallow bugs at cliff swallow colonies in Nebraska and Colorado in the summer of 2001 and were compared with the corresponding region of BCRV isolates collected from Oklahoma in the 1980s. We also analyzed isolates of the closely related Fort Morgan virus (FMV) collected from Colorado in the 1970s. Phylogenetic analysis indicated that BCRV falls into the western equine encephalomyelitis complex of alphaviruses, in agreement with antigenic results and a previous alphavirus phylogeny based on the E1 coding region. We found four distinct BCRV/FMV clades, one each unique to Nebraska, Colorado, and Oklahoma and one containing isolates from both Nebraska and Colorado. BCRV isolates within the two clades from Nebraska showed 5.7 to 6.2% nucleotide divergence and 0.7 to 1.9% amino acid divergence, and within these clades, we found multiple subclades. Nebraska subclades tended to be confined to one or a few cliff swallow colonies that were close to each other in space, although in some cases, near-identical isolates were detected at sites up to 123 km apart. Viral gene flow occurs when cliff swallows move (bugs) between colony sites, and the genetic structure of BCRV may reflect the limited dispersal abilities of its insect vector.

Alphavirus↗
PubMed1994

Detection of bluetongue virus in the blood of inoculated calves: comparison of virus isolation, PCR assay, and in vitro feeding of Culicoides variipennis.

The interval after infection when bluetongue virus (BTV) was present in the blood of calves inoculated with BTV serotype 10 (BTV 10) was evaluated by virus isolation (VI) in embryonated chicken eggs (ECE), BTV-specific polymerase chain reaction (PCR), and in vitro blood feeding of vector Culicoides variipennis (C.v.) sonorensis. BTV nucleic acid was detected by PCR in blood cells for 16 to 20 weeks after infection whereas infectious virus was detected by VI in ECE for 2 to 8 weeks. BTV was detected in calf blood by in vitro feeding of C.v. sonorensis for only 0 to 2 weeks after inoculation of calves with BTV 10. Selected bloods which were positive by PCR analysis but not by VI in ECE were not infectious for sheep. The data are consistent with the hypothesis that prolonged viremia in BTV-infected cattle results from association of the virus with blood cells, especially erythrocytes. The fact that calf blood that contained viral nucleic acid as determined by PCR analysis, but not infectious virus as determined by VI in ECE, was not infectious for either the insect vector or sheep suggests that cattle whose blood contains BTV nucleic acid but not infectious virus are unimportant to the epidemiology of BTV infection.

Animals↗
PubMed2003

'Candidatus phytoplasma ziziphi', a novel phytoplasma taxon associated with jujube witches'-broom disease.

Phylogenetic relationships of five jujube witches'-broom (JWB) phytoplasma isolates from four different districts, and other phytoplasmas, were investigated by 16S rDNA PCR amplification and sequence analysis. The 16S rDNA sequences of any pair of the five isolates of JWB phytoplasmas were > 99.5% similar. The JWB phytoplasma 16S rDNA sequences were most closely related to that of the elm yellows (EY) phytoplasma in 16S-group VIII. Phylogenetic analysis of the 16S rDNA sequences from the JWB phytoplasma isolates, together with sequences from most of the phytoplasmas archived in GenBank, produced a tree in which the JWB isolates clustered as a discrete subgroup. The uniqueness of the JWB phytoplasma appears to be correlated with a specific insect vector (Hishimonus sellatus) and the host plant (Zizyphus jujuba), or with a specific geographical distribution. The unique properties of the JWB phytoplasma sequences clearly indicate that it represents a novel taxon, 'Candidatus Phytoplasma ziziphi'.

Acholeplasmataceae↗
PubMedDate not supplied

Transmission ecology of the fly Musca sorbens, a putative vector of trachoma.

Recent evidence suggests that eye-seeking flies are important trachoma vectors. We conducted a series of investigations to identify which species of synanthropic flies are potential vector(s) of this blinding disease in The Gambia. Several species of fly were caught in fish-baited attractant traps placed in villages throughout the year (1997/98) but only 2 species, Musca sorbens and M. domestica, were caught from the eyes of children. M. sorbens comprised < 10% of the total number of flies caught with attractant traps but was responsible for > 90% of fly-eye contacts, the remainder were made by M. domestica. All fly species were more numerous in the wet season than the dry season. Eyes of young children are considered to be the main reservoir of Chlamydia trachomatis, the causative agent of trachoma. Collections of eye-seeking flies from children showed frequent fly-eye contacts (median [interquartile range], 3 [1.5-7] every 15 min). Children with potentially infective ocular or nasal discharge had twice as many fly-eye contacts than children with no discharge (P < 0.001). There was no difference in exposure to fly-eye contacts if a child sat inside or outside a house (P = 0.273). Female flies were more commonly caught from eyes than male (P < 0.001). The presence of Chlamydia DNA was demonstrated by PCR on 2 of 395 flies caught from the eyes of children with a current active trachoma infection. Both positive flies were M. sorbens, one male and the other female. Further elucidation of M. sorbens behavioural ecology and the development of sustainable strategies to control these flies should be a priority. It is likely that M. sorbens is the principal insect vector of trachoma in The Gambia.

Animals↗
PubMed1997

Trypanosoma cruzi: specific detection of parasites by PCR in infected humans and vectors using a set of primers (BP1/BP2) targeted to a nuclear DNA sequence.

In the present work we evaluate Trypanosoma cruzi DNA detection by PCR using the nuclear oligonucleotides BP1/BP2 as primers. These primers are targeted to the 5' and 3' ends of the coding region for the flagellar protein F29. An amplification product of BP1/BP2 is a DNA band 692 bp long. Titration assays were performed to evaluate the minimum amount of parasite DNA that can be detected by this assay, resulting in 10 fg (equivalent to about 1/20 of the genome). The assay was also performed using T. cruzi DNA from different strains, clones, and human-derived isolates obtaining, in all cases, amplification products. No DNA amplification was observed when the PCR was performed using DNA from Leishmania braziliensis, but when T. rangeli DNA was used, a 615-bp-long fragment was amplified. Under appropriate gel conditions T. cruzi and T. rangeli DNA amplicons could be differentiated. When both conventional xenodiagnosis and PCR detection of parasite DNA in the feces of insect vectors fed with blood from infected patients were compared, 10 of 20 samples were positive by both techniques. However, 2 other samples with positive serology were also positive by PCR. When PCR was performed on blood samples from infected and uninfected individuals, 62 of 65 serologically positive human samples amplified the BP1/BP2 692-bp T. cruzi DNA fragment (sensitivity >95%). The 3 negative samples were positive when Southern blot hybridization was performed using the radiolabeled PCR amplification product as probe (sensitivity 100%).

Animals↗
PubMed2005

Identification of naturally infected Lutzomyia intermedia and Lutzomyia migonei with Leishmania (Viannia) braziliensis in Rio de Janeiro (Brazil) revealed by a PCR multiplex non-isotopic hybridisation assay.

To identify naturally infected Lutzomyia spp. by Leishmania (Viannia) braziliensis, a PCR multiplex non-isotopic hybridisation assay was developed for the analysis of insect samples collected in distinct areas of the municipality of Rio de Janeiro (Brazil), from March to December 2003. Data from experimental infection indicate that the method can detect one individual infected insect out of ten. Wild sand flies were classified and grouped into pools of 10 specimens each, reaching a total of 40 female groups. Positive results were obtained with pools of Lu. intermedia (5/32) and Lu. migonei (3/5) collected in two areas from the district of Jacarepaguá presenting recent cases of human and canine leishmaniasis. Considering eight infected groups (8/40) with at least one positive insect in each, it was possible to infer an infection rate of 2%. This technique permits the synchronous processing of a large number of samples, in order to investigate infection rates in sand fly populations and to identify potential insect vectors. The results presented here represent the first molecular approach used to infer the natural infection index in both Lutzomyia spp. and constitute essential data to the understanding of leishmaniasis ecoepidemiology in endemic areas from Rio de Janeiro.

Animals↗
PubMed2003

Identification and characterization of phytoplasmal genes, employing a novel method of isolating phytoplasmal genomic DNA.

Phytoplasmas are unculturable, insect-transmissible plant pathogens belonging to the class Mollicutes. To be transmitted, the phytoplasmas replicate in the insect body and are delivered to the insect's salivary glands, from where they are injected into the recipient plant. Because phytoplasmas cannot be cultured, any attempt to recover phytoplasmal DNA from infected plants or insects has resulted in preparations with a large background of host DNA. Thus, studies of the phytoplasmal genome have been greatly hampered, and aside from the rRNA genes, only a few genes have hitherto been isolated and characterized. We developed a unique method to obtain host-free phytoplasmal genomic DNA from the insect vector's saliva, and we demonstrated the feasibility of this method by isolating and characterizing 78 new putative phytoplasmal open reading frames and their deduced proteins. Based on the newly accumulated information on phytoplasmal genes, preliminary characteristics of the phytoplasmal genome are discussed.

Animals↗
PubMed2003

Animals, disease, and man: making connections.

The intricate causal relationships between disease in man and disease in animals first began to be elucidated in the mid-19th century. Although the connections between animal and human disease are now generally understood, individuals as well as societies remain slow to act on this knowledge. This paper examines the gradual recognition of these disease connections and explores the parallel theme of man's reluctance to appreciate the implications of these connections. It identifies factors that have inhibited the realization of the links between disease in man and animals, and discusses several milestones in the scientific elucidation of these links. Beginning with emerging concerns over the relationship between bovine and human tuberculosis in the 1860s, it follows the discovery of insect vectors, animal reservoirs, and the links between animals, influenza, and man. Despite warnings of the potential significance for human disease of patterns of changes in the relationship with animals and the natural world, scientists have continued to treat human and animal health as largely independent disciplines, while historians too have neglected this important aspect of human disease.

Animals↗