Ferritin in insect vectors of the maize streak disease agent: electron microscopy and electron microprobe analysis.
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Animals↗
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Results for “Insect Vectors”
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[Role of insect vectors in the transmission of HBsAg].
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Anopheles↗
Small interfering RNAs generated from the terminal panhandle structure of negative-strand RNA virus promote viral infection.
Virus-derived small interfering RNAs (vsiRNAs) have been widely recognized to play an antiviral immunity role. However, it is unclear whether vsiRNAs can also play a positive role in viral infection. Here, we characterized three highly abundant vsiRNAs mapped to the genomic termini of rice stripe virus (RSV), a negative-strand RNA virus transmitted by insect vectors. The three vsiRNAs shared 11 nucleotides due to the conservative genomic termini and were likely generated from viral terminal panhandle structure, depending on both Dicer1 and Dicer2 in insects. In addition to targeting viral RNAs in a miRNA-like manner, the three vsiRNAs coordinately downregulated the expression of DOPA decarboxylase, thereby suppressing the prophenoloxidase immune reaction in insect vectors. In vsiRNA-silenced transgenic rice, the viral titer significantly decreased, indicating that these vsiRNAs promote RSV replication in rice. This study elucidates a unique function of vsiRNAs derived from the conserved panhandle structure of negative-strand RNA viruses in enhancing viral infection.
RNA, Small Interfering↗
Insecticide susceptibility of some vector fleas and mosquitoes in Burma.
Rat fleas and mosquitoes are insect vectors of public health importance in Burma. Plague is endemic in Central Burma and DDT has been the principal insecticide used for its control to date. Dengue haemorrhagic fever, recently introduced and transmitted by Aedes aegypti, has been spreading to major towns since 1971. The rodents, Rattus rattus, R. exulans, Bandicota bengalensis, Mus musculus, as well as shrews were commonly caught during routine trapping in the country. Rattus norvegicus, prevalent in Rangoon City, is not found in Central Burma. The rat fleas, Xenopsylla cheopis and X. astia, were found to be infesting these rodents, the former being the principal vector of plague. Insecticide susceptibility tests have been carried out periodically in plague endemic areas and Rangoon since 1966 and it is now observed that rat fleas in most of these endemic towns and Rangoon Port are no longer susceptible to DDT. Subsequent rechecks in towns where fleas became resistance to DDT show that fleas are persistently resistant to the insecticide. Aedes aegypti is found to be highly prevalent both in rural and urban areas of almost every major town and townships below 900 meters. Insecticide susceptible tests on this mosquito in limited areas show that the mosquito is generally resistant to DDT but susceptible to other insecticides. With the development of DDT resistance in fleas, it is now necessary to change to an effective insecticide in the control of plague in Burma.
Aedes↗
Phytoplasma-plant interactions: effector-mediated host reprogramming, hormonal crosstalk, metabolic alterations and plant-mediated vector manipulation.
Phytoplasmas are wall-less, phloem-restricted bacterial pathogens that infect over 1,000 plant species, causing substantial losses in agriculture, horticulture, and forestry worldwide. Despite their reduced genomes and limited metabolic autonomy, these obligate parasites colonize diverse hosts through secreted effector proteins that extensively reprogram plant development, metabolism, immune signalling, and vector interactions. Advances in genomics, transcriptomics, proteomics, metabolomics, and functional studies have substantially clarified the molecular basis of phytoplasma pathogenicity and symptom development. This review synthesizes current understanding of phytoplasma-plant interactions, covering phytoplasma biology, genome evolution, and the infection cycle across plant and insect vector hosts. We examine the molecular functions of key effectors, SAP11, SAP54/PHYL1, SAP05, TENGU, SWP1, and recently identified virulence factors, focusing on how they target host transcription factors, phytohormone networks, protein degradation pathways, and immune responses to promote colonization and disease progression. We further discuss how phytoplasma infection disrupts phytohormone signalling, primary and secondary metabolism, and developmental programs to produce characteristic disease symptoms, with particular attention to pathogen-induced changes in host volatiles and nutritional quality that alter vector behaviour and enhance transmission. Finally, we summarize insights from multi-omics studies and emerging management strategies, including CRISPR-based genome editing, RNAi, rapid molecular diagnostics, resistant cultivars, microbiome-based approaches, and sustainable vector control, and highlight key knowledge gaps and priorities for developing effective, environmentally sustainable phytoplasma disease management.
Phytoplasma↗
Epizootiology of bluetongue: the situation in the United States of America.
Bluetongue was first reported in the United States in 1948 in sheep in Texas. The virus has now been isolated from sheep in 19 States. When the disease first occurs in a flock, the morbidity may reach 50 to 75% and mortality 20 to 50%. In subsequent years, the morbidity may be only 1 to 2% with very few deaths. Difference in breed susceptibility has not been observed. Natural bluetongue infection has not been observed in Angora or dairy goats. Bluetongue virus was first isolated from cattle, in Oregon, in 1959. The virus has now been isolated from cattle in 13 States. In cattle, the disease is usually inapparent but can cause mild to severe clinical disease and neonatal losses. Natural clinical bluetongue has also been reported in bighorn sheep, exotic ruminants in a zoo, mule deer, and white-tailed deer. Serological evidence of exposure to the virus has also been found in other species of ruminants in the wild. Inoculation of virulent bluetongue virus, vaccine virus, or natural disease can cause congenital deformities and neonatal losses in calves, lambs, and white-tailed deer fawns. Culicoides is considered the important insect vector of bluetongue. The virus has also been isolated from sheep keds and cattle lice. U.S. field strains of the virus fit into four serologic groups. No cross reactions were found between bluetongue and epizootic haemorrhagic disease of deer viruses. Cattle are considered significant virus reservoirs. It is necessary to use washed erythrocytes, rather than whole blood, and to inoculate susceptible sheep, rather than embryonated chicken eggs, to detect longer-term viraemia in cattle.
Animals↗
The epizootiology of bluetongue: the African situation.
Bluetongue virus is transmitted biologically by various species of Culicoides, notably C. pallidipennis and C. variipennis. Factors such as rainfall, temperature and relative altitude, which influence the breeding of the insect vectors also govern the incidence and distribution of the disease. The host range of bluetongue virus includes sheep, cattle, goats and various antelopes. Many other, as yet unidentified hosts could perhaps harbour the virus and influence the epizootiology of the disease. The close relationship between C. pallidipennis and cattle is indicated and the efficient mechanism for virus maintenance which this relationship constitutes is emphasised. It is further postulated that sheep are not essential for the continued survival of bluetongue virus, but merely function as accidental or indicator hosts.
Africa, Southern↗
The control of bluetongue in an enzootic situation.
On account of the wide host range of bluetongue virus and its biological transmission by insects, control of the disease in an enzootic situation is based primarily on the active immunisation of susceptible animals as well as on the prevention of contact between the insect vectors and the susceptible hosts. In spite of their unquestionable value, the egg attenuated vaccines which are currently employed for prophylactic immunisation, have certain shortcomings. The existence of 16 known serotypes of bluetongue virus makes it difficult to achieve a very wide spectrum of immunity in sheep vaccinated once or twice only. The problems which are experienced with the immunisation of lambs born in spring are indicated. The present vaccine can also present problems when used in breeding animals. Furthermore, the costs involved in the annual vaccination of large numbers of animals are considerable. The need for a vaccine for cattle is indicated. Work is also being conducted at present on the development of an inactivated vaccine for use in sheep. The use of novel virological techniques may aid in the future development of absolutely safe and highly efficient vaccines against bluetongue.
Animals↗
Human sleeping sickness in the Gboko endemic area of Nigeria.
Human infection with Trypanosoma gambiense in the Gboko endemic area was first reported in May, 1974 although T. gambiense sleeping sickness had been present there since the turn of the century. The disease is associated with the presence of the tsetse Glossina tachinoides and Glossina palpalis which is plentiful and widespread throughout the division as well as in thickets along the streams in the area. No successful attempt has been made to control the tsetse vector in the Division. The incidence and geographical distribution of cases of T. gambiense sleeping sickness in the Gboko area are described in this report. Cases were treated with Antrypol Tryparsamide mixture and Mel B. The highest number of cases of infection is usually picked up just before the start of the rains in early April. It is suggested that, for meaningful control of the disease a quick method should be devised to rid the area of the insect vector.
Humans↗
Incidence of bluetongue virus precipitating antibodies in sera of some domestic animals in the Sudan.
To determine the presence and prevalence of bluetongue (BT) infection in a variety of domestic animal species in different geographical regions of the Sudan, a serological study using the agar gel precipitation technique was initiated. A total of 2142 serum samples were examined. Of the numbers tested approximately 28% of sheep, 11.2% of goats, 8% of cattle and 4.9% of camels were positive for group-specific antibodies to BT virus antigen, indicating previous exposure to BT infection. None of the samples tested from horses or donkeys were positive. The findings suggest that the disease is widely distributed in most parts of the Sudan where possible insect vectors prevail and may be endemic in sheep in Juba District, Equatoria Province, Southern Region. Goats appeared to have some degree of resistance to infection compared with sheep, and there seemed to be no significant differences in positive rates between farm and free-range cattle. It is concluded that BT infection may cause clinical disease in sheep, while it is probably subclinical or inapparent in goats, cattle and camels of the Sudan.
Animals↗
Degradation of ribosomal RNA during Plasmodium falciparum gametocytogenesis.
The life cycle of Plasmodium falciparum is characterized by complex regulatory changes that allow adaptation of the parasites to different environmental conditions, which are especially pronounced during transmission between the mammalian host and the insect vector. Previous studies have shown that P. falciparum uses three types of ribosomal RNAs (rRNA A, S1, and S2 types) at different stages of its life cycle. We used Oxford Nanopore Technologies direct RNA sequencing to investigate the dynamics of rRNA usage throughout the parasite's intraerythrocytic development, as well as in salivary gland sporozoites. Our study revealed a preponderance of A-type rRNAs during the intraerythrocytic cycle and gametocytogenesis, while S-type rRNAs slowly increase in abundance in mosquito stages starting 3 days post-infection. Salivary gland sporozoites showed an even proportion of all rRNA types. By examining the length distributions of rRNA molecules, we detected an extensive and specific degradation of rRNAs during gametocytogenesis, starting in stage II gametocytes and continuing until the final stages of gametocyte development. We hypothesize that rRNA degradation may be linked to the global translational repression and metabolic quiescence described in stage V gametocytes, similar to mechanisms observed in bacterial and eukaryotic stress responses.IMPORTANCEOur study uses Oxford Nanopore direct RNA sequencing of tightly synchronized blood-stage Plasmodium falciparum parasites to investigate the expression of ribosomal RNAs during asexual and sexual development. P. falciparum utilizes distinct types of rRNA during its development. However, due to the challenges of differentiating these highly similar molecules, their regulation and the mechanism underlying the switch between rRNA types remain unclear. We observe significant rRNA degradation in mature gametocytes, leading us to propose that this potentially leads to a reduced number of functional ribosomes when parasites become quiescent and translation is repressed.
Plasmodium falciparum↗
Phylogenetics and genomic variation of Hepatocystis isolated from shotgun sequencing of wild primate hosts.
Hepatocystis are apicomplexan parasites nested within the Plasmodium genus that infect primates and other vertebrates, yet few isolates have been genetically characterized. Using taxonomic classification and mapping characteristics, we searched for Hepatocystis infections within publicly available, blood-derived whole genome sequence (WGS) data from 326 wild non-human primates (NHPs) in 17 genera. We identified 37 Hepatocystis infections in Papio cynocephalus (yellow baboons) and four species of Chlorocebus monkeys (grivets, green monkeys, vervet monkeys, and malbroucks) sampled from locations in west, east, and south Africa. Hepatocystis cytb sequences from Papio and Chlorocebus hosts each clustered within host species among previously reported isolates from other NHP taxa. Utilizing the low-coverage sequence data (0.11-0.76X per sample) recovered across the nuclear Hepatocystis genome, we identified 349,893 polymorphic sites. Principle components analysis based on genotype likelihoods across all samples showed evidence for population structure by primate host species. Across the genome, windows of high SNP density revealed candidate hypervariable loci including Hepatocystis-specific gene families possibly involved in immune evasion and genes that may be involved in adaptation to their insect vector and hepatocyte invasion. Overall, this work demonstrates how WGS data from wild NHPs can be leveraged to study the evolution of apicomplexan parasites and potentially test for association between host genetic variation and parasite infection.
Animals↗
Temporal appearance, geographic distribution, and species of origin of bluetongue virus serotypes in the United States.
Beginning in 1973, all available laboratory and field strains of bluetongue virus (BTV) from the United States were serotyped. Of the viral strains serotyped, 27 were collected from 1953 through 1972; 173 were collected from 1973 through 1977. Although 20 BTV serotypes have been found worldwide, only BTV serotypes 10, 11, 13, and 17 have been found in the United States. Since 1973, serotypes 11 and 17 have been the prevalent serotypes. Samples were collected over a 24-year period in the United States and represent a wide geographic area and diverse host sources (sheep, cattle, wild ruminants, and insect vectors). The collection was not a statistical sampling.
Animals↗
[Epidemiology and the prevention of zoonotic cutaneous leishmaniasis].
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Afghanistan↗
Spiroplasma endosymbiont reduction of host lipid synthesis and Stomoxyn-like peptide contribute to trypanosome resistance in the tsetse fly Glossina fuscipes.
Tsetse flies (Glossina spp.) vector African trypanosomes that cause devastating diseases in humans and domestic animals. Within the Glossina genus, species in the Palpalis subgroup exhibit greater resistance to trypanosome infections compared to those in the Morsitans subgroup. Varying microbiota composition and species-specific genetic traits can significantly influence the efficiency of parasite transmission. Notably, infections with the endosymbiotic bacterium Spiroplasma have been documented in several Palpalis subgroup species, including Glossina fuscipes fuscipes (Gff). While Spiroplasma infections in Gff are known to hinder trypanosome transmission, the underlying mechanisms remain unknown. To investigate Spiroplasma-mediated factors affecting Gff vector competence, we conducted high-throughput RNA sequencing of the gut tissue along with functional assays. Our findings reveal elevated oxidative stress in the gut environment in the presence of Spiroplasma, evidenced by increased expression of nitric oxide synthase, which catalyzes the production of trypanocidal nitric oxide. Additionally, we observed impaired lipid biosynthesis leading to a reduction of this important class of nutrients essential for parasite and host physiologies. In contrast, trypanosome infections in Gff's midgut significantly upregulated various immunity-related genes, including a small peptide, Stomoxyn-like, homologous to Stomoxyn first discovered in the stable fly, Stomoxys calcitrans. We observed that the Stomoxyn-like locus is exclusive to the genomes of Palpalis subgroup tsetse species. GffStomoxyn is constitutively expressed in the cardia (proventriculus) and synthetic GffStomoxyn exhibits potent activity against Escherichia coli and bloodstream form of Trypanosoma brucei parasites, while showing no effect against insect stage procyclic forms or tsetse's commensal endosymbiont Sodalis in vitro. Reducing GffStomoxyn levels significantly increased trypanosome infection prevalence, indicating its potential trypanocidal role in vivo. Collectively, our results suggest that the enhanced resistance to trypanosomes observed in Spiroplasma-infected Gff may be due to the reduced lipid availability necessary for parasite metabolic maintenance. Furthermore, GffStomoxyn could play a crucial role in the initial immune response(s) against mammalian parasites early in the infection process in the gut and prevent gut colonization. We discuss the molecular characteristics of GffStomoxyn, its spatial and temporal expression regulation and its microbicidal activity against Trypanosome parasites. Our findings reinforce the nutritional influences of microbiota on host physiology and host-pathogen dynamics.
Animals↗
Arboviruses and their vectors in India.
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Animals↗
[Use of radioactive isotopes in medical parasitology (review of the literature)].
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Animals↗
A deep insight into the sialome of the house fly, Musca domestica, infected with the salivary gland hypertrophy virus (MdSGHV).
The house fly, Musca domestica, serves as a mechanical vector for numerous pathogens, posing a significant risk to human and animal health. More than two decades ago, the Musca domestica salivary gland hypertrophy virus (MdSGHV) was discovered, infecting both males and females flies and disrupting mating and the reproductive process. While MdSGHV can infect various tissues, its primary replication site is the house fly salivary gland. It is well established that arthropod salivary glands play an important role not only in acquiring food but also in transmitting pathogens. Therefore, understanding the composition of vector salivary glands and the interactions between vector and pathogen components is essential for developing future control strategies. To this end, we conducted a comprehensive RNA-sequencing of salivary glands from both infected and non-infected house flies. Our analysis identified a total of 6,410 putative sequences, with 6,309 originating from M. domestica and 101 from the MdSGHV, categorized into 25 functional groups. Furthermore, differential expression analysis between infected and non-infected salivary glands revealed 2,852 significantly modulated transcripts, highlighting profound transcriptional changes triggered by MdSGHV infection. Overall, these findings not only deepen our understanding of the composition of M. domestica salivary glands but also provide valuable insight into the virus-vector interaction, which could serve as a model to understand other medically relevant interactions.
Salivary Glands↗