Rickettsiaceae
Ehrlichia ruminantium
Rickettsia
Symbiosis
RNA, Ribosomal, 16S
Wolbachia
Asia, Southeastern
Malaria
Anopheles gambiae
Relative virulence of three isolates of Piscirickettsia salmonis for coho salmon Oncorhynchus kisutch. (1/100)
Piscirickettsia salmonis was first recognized as the cause of mortality among pen-reared coho salmon Oncorhynchus kisutch in Chile. Since the initial isolation of this intracellular Gram-negative bacterium in 1989, similar organisms have been described from several areas of the world, but the associated outbreaks were not reported to be as serious as those that occurred in Chile. To determine if this was due to differences in virulence among isolates of P. salmonis, we conducted an experiment comparing isolates from Chile, British Columbia, Canada, and Norway (LF-89, ATL-4-91 and NOR-92, respectively). For each of the isolates, 3 replicates of 30 coho salmon were injected intraperitoneally with each of 3 concentrations of the bacterium. Negative control fish were injected with MEM-10. Mortalities were collected daily for 41 d post-injection. Piscirickettsiosis was observed in fish injected with each of the 3 isolates, and for each isolate, cumulative mortality was directly related to the concentration of bacterial cells administered. The LF-89 isolate was the most virulent, with losses reaching 97% in the 3 replicates injected with 10(5.0) TCID50, 91% in the replicates injected with 10(4.0) TCID50, and 57% in the fish injected with 10(3.0) TCID50. The ATL-4-91 isolate caused losses of 92% in the 3 replicates injected with 10(5.0) TCID50, 76% in the fish injected with 10(4.0) TCID50, and 32% in those injected with 10(3.0) TCID50. The NOR-92 isolate was the least virulent, causing 41% mortality in the replicates injected with 10(4.6) TCID50. At 41 d post-injection, 6% of the fish injected with 10(3.6) TCID50 NOR-92 had died. Mortality was only 2% in the fish injected with 10(2.6) TCID50 NOR-92, which was the same as the negative control group. Because the group injected with the highest concentration (10(4.6) TCID50) of NOR-92 was still experiencing mortality at 41 d, it was held for an additional 46 d. At 87 d post-injection, the cumulative mortality in this group had reached 70%. These differences in virulence among the isolates were statistically significant (p < 0.0001), and are important for the management of affected stocks of fish. (+info)Routes of entry of Piscirickettsia salmonis in rainbow trout Oncorhynchus mykiss. (2/100)
Since 1989, Piscirickettsia salmonis, the causal agent of piscirickettsiosis, has killed millions of farmed salmonids each year in southern Chile. The portal of entry for the pathogen was investigated by use of selected experimental infections in juvenile rainbow trout (12 g). The methods used were intraperitoneal injection, subcutaneous injection, patch contact on skin, patch contact on gills, intestinal intubation and gastric intubation. Cumulative mortalities at Day 33 post-inoculation were 98, 100, 52, 24, 24, and 2%, respectively. It was shown that intact skin and gills could be penetrated by P. salmonis. The high mortality obtained in subcutaneously injected fish indicated that skin injuries could facilitate the invasion of this pathogen. Results suggested that the main entry sites are through the skin and gills and that the oral route may not be the normal method by which P. salmonis initiates infection of salmonids. (+info)Pathogenesis of liver lesions caused by experimental infection with Piscirickettsia salmonis in juvenile Atlantic salmon, Salmo salar L. (3/100)
Piscirickettsia salmonis, the etiologic agent of salmonid rickettsial septicemia (SRS), or piscirickettsiosis, causes substantial economic losses to the salmon industry. The pathogenesis of the disease has not been fully characterized. The aim of this study is to describe the hepatic lesions associated with experimental P. salmonis infection in Atlantic salmon juveniles. Fish were maintained in fresh water and inoculated intraperitoneally (IP), orally, or on the gill surface with P. salmonis. A group of uninfected fish was kept as control. Liver samples from 5 fish in each inoculated group and 3 controls were collected weekly and processed for histological and immunohistochemical examination. Thickening of the liver capsule by inflammatory cells was a characteristic histologic feature of IP inoculated fish. Three weeks post-IP inoculation, 8 fish had died and 2 fish were sampled. Histological changes at this time consisted of vasculitis, presence of fibrin thrombi, vacuolated hepatocytes and focal areas of necrosis. Leukocytes containing intracytoplasmic basophilic microorganisms were seen within hepatic sinusoids. Vasculitis and intracytoplasmic vacuoles were prominent features in fish inoculated orally and on the gill surface. The presence of P. salmonis within hepatocellular vacuoles, endothelial cells, and leucocytes was confirmed by immunohistochemistry. The intracellular location of P. salmonis and the vascular damage seen in infected fish are characteristic of rickettsial infections. Histological lesions induced by experimental infection with P. salmonis using the oral and gill surface routes were similar to those observed in natural outbreaks of piscirickettsiosis. The tropism of P. salmonis for endothelial cells explains the vascular lesions observed in SRS, whereas hepatic lesions are due to ischemic necrosis and direct injury by intracytoplasmic organisms. (+info)In vitro activity of antimicrobial agents against the endosymbiont Wolbachia pipientis. (4/100)
Arthropod-transmitted (filarial) nematodes are important causes of disease in humans in tropical countries, yet no safe drug appropriate for mass delivery kills the adult worms. However, most filarial nematodes contain rickettsia-like bacteria of the genus Wolbachia, and related bacteria also occur in insects. There is increasing evidence that these bacteria have significant functions in the biology of filarial nematodes. They are thus important targets in the search for antifilarial drugs and experiments in animals and humans have suggested that antibiotic therapy has potential in treating filarial infections. To optimize future clinical trials there is a need for a fast and simple in vitro drug screen to compare drug efficacies against Wolbachia. In the absence of Wolbachia-infected nematode cell lines, we have utilized an Aedes albopictus insect cell line, naturally infected with Wolbachia, to test the activity of antimicrobial agents. Of the five antibiotics tested, doxycycline, oxytetracycline and rifampicin showed good activity (MICs of 0.0625, 4 and 0.0625 mg/L, respectively) whereas ciprofloxacin and penicillin were shown to have no effect. (+info)Platelet kinetics in canine ehrlichiosis: evidence for increased platelet destruction as the cause of thrombocytopenia. (5/100)
A significant (P < 0.025) increase in the mean platelet diameter occurred in five Ehrlichia canis-infected dogs when platelet numbers decreased to 100,000/mul or less. Maximal incorporation of [(75)Se]selenomethionine into platelets of six uninfected dogs was 0.080 +/- 0.019% (mean +/- standard error) and occurred 5 to 6 days after dosage, whereas maximal incorporation was 0.036 +/- 0.004% within 2 to 3 days after dosage in seven chronically infected dogs that had thrombocytopenia. Analysis of the [(75)Se]selenomethionine curves yielded a platelet lifespan of 9 days in uninfected dogs versus 4 days in chronically infected dogs. Thus, megakaryocyte maturation and/or platelet release occurred at an accelerated rate in infected dogs, whereas increased destruction of newly produced labeled platelets diminished their number of peripheral blood. [(51)Cr]sodium chromate-labeled platelet survival was exponential, with a half-life of approximately 1 day in two dogs at 2 to 4 days postinfection and three chronically infected dogs. Platelet survival time was 8 days and rectilinear in four uninfected dogs. Platelet recovery was 39.43 +/- 2.86% in infected dogs as compared with 68.2 +/- 10.72% in uninfected dogs. Whole-body scans of one dog prior to and 7 days after infection showed that labeled platelets were destroyed primarily in the spleen. It is concluded that the thrombocytopenia in E. canis-infected dogs is the result of increased platelet destruction which begins within a few days after infection. (+info)Molecular analysis of Neorickettsia risticii in adult aquatic insects in Pennsylvania, in horses infected by ingestion of insects, and isolated in cell culture. (6/100)
Upon ingestion of adult aquatic insects, horses developed clinical signs of Potomac horse fever, and Neorickettsia risticii was isolated from the blood. 16S rRNA and 51-kDa antigen gene sequences from blood, isolates, and caddis flies fed to the horses were identical, proving oral transmission of N. risticii from caddis flies to horses. (+info)The effect of Wolbachia-induced cytoplasmic incompatibility on host population size in natural and manipulated systems. (7/100)
Obligate, intracellular bacteria of the genus Wolbachia often behave as reproductive parasites by manipulating host reproduction to enhance their vertical transmission. One of these reproductive manipulations, cytoplasmic incompatibility, causes a reduction in egg-hatch rate in crosses between individuals with differing infections. Applied strategies based upon cytoplasmic incompatibility have been proposed for both the suppression and replacement of host populations. As Wolbachia infections occur within a broad range of invertebrates, these strategies are potentially applicable to a variety of medically and economically important insects. Here, we examine the interaction between Wolbachia infection frequency and host population size. We use a model to describe natural invasions of Wolbachia infections, artificial releases of infected hosts and releases of sterile males, as part of a traditional sterile insect technique programme. Model simulations demonstrate the importance of understanding the reproductive rate and intraspecific competition type of the targeted population, showing that releases of sterile or incompatible individuals may cause an undesired increase in the adult number. In addition, the model suggests a novel applied strategy that employs Wolbachia infections to suppress host populations. Releases of Wolbachia-infected hosts can be used to sustain artificially an unstable coexistence of multiple incompatible infections within a host population, allowing the host population size to be reduced, maintained at low levels, or eliminated. (+info)Rickettsialpox in North Carolina: a case report. (8/100)
We report a case of rickettsialpox from North Carolina confirmed by serologic testing. To our knowledge, this case is the first to be reported from this region of the United States. Including rickettsialpox in the evaluation of patients with eschars or vesicular rashes is likely to extend the recognized geographic distribution of Rickettsia akari, the etiologic agent of this disease. (+info)Rickettsiaceae is a family of Gram-negative, obligate intracellular bacteria that are primarily parasitic in arthropods and mammals. They are the causative agents of several important human diseases, including typhus fever, Rocky Mountain spotted fever, and rickettsialpox. These bacteria are typically transmitted to humans through the bites of infected arthropods such as ticks, fleas, or lice.
The bacteria in Rickettsiaceae are small, non-motile, and have a unique bipolar appearance with tapered ends. They can only replicate inside host cells, where they manipulate the host cell's machinery to create a protective niche for themselves. This makes them difficult to culture and study outside of their hosts.
Rickettsiaceae bacteria are divided into several genera based on their genetic and antigenic characteristics, including Rickettsia, Orientia, and Coxiella. Each genus contains several species that can cause different diseases in humans. For example, Rickettsia rickettsii is the causative agent of Rocky Mountain spotted fever, while Rickettsia prowazekii causes epidemic typhus.
Overall, Rickettsiaceae bacteria are important pathogens that can cause serious and sometimes fatal diseases in humans. Prompt diagnosis and treatment with appropriate antibiotics is essential for a successful outcome.
Rickettsiaceae is a family of Gram-negative, aerobic, intracellular bacteria that includes several important human pathogens. Rickettsiaceae infections are diseases caused by these bacteria, which include:
1. Rocky Mountain Spotted Fever (RMSF): Caused by Rickettsia rickettsii and transmitted to humans through the bite of infected ticks. The disease is characterized by fever, headache, muscle pain, and a rash that spreads from the wrists and ankles to the trunk.
2. Epidemic Typhus: Caused by Rickettsia prowazekii and transmitted to humans through the feces of infected lice. The disease is characterized by fever, headache, muscle pain, and a rash that starts on the chest and spreads to the rest of the body.
3. Murine Typhus: Caused by Rickettsia typhi and transmitted to humans through the feces of infected fleas. The disease is characterized by fever, headache, muscle pain, and a rash that starts on the trunk and spreads to the limbs.
4. Scrub Typhus: Caused by Orientia tsutsugamushi and transmitted to humans through the bite of infected chiggers. The disease is characterized by fever, headache, muscle pain, and a rash that starts on the trunk and spreads to the limbs.
5. Rickettsialpox: Caused by Rickettsia akari and transmitted to humans through the bite of infected mites. The disease is characterized by fever, headache, muscle pain, and a rash that starts as papules and becomes vesicular.
These infections are treated with antibiotics such as doxycycline or chloramphenicol. Early diagnosis and treatment are crucial to prevent severe complications and death.
'Ehrlichia ruminantium' is a gram-negative, intracellular bacterium that belongs to the family Anaplasmataceae. It is the etiological agent of heartwater, a tick-borne disease that affects mainly ruminants such as cattle, sheep, and goats. The bacteria infect endothelial cells in various organs, including the brain and heart, causing vasculitis, edema, and hemorrhage, which can lead to severe clinical signs and death in infected animals.
The bacterium is transmitted through the bite of infected ticks, mainly from the genus Amblyomma. The disease is endemic in many tropical and subtropical regions of the world, including Africa, the Caribbean, and South America. Heartwater is a major constraint to livestock production in affected areas, causing significant economic losses to farmers and pastoralists.
Prevention and control measures for heartwater include the use of acaricides to control tick infestations, vaccination of susceptible animals, and quarantine measures to prevent the introduction of infected animals into disease-free areas.
Rickettsia is a genus of Gram-negative, aerobic, rod-shaped bacteria that are obligate intracellular parasites. They are the etiologic agents of several important human diseases, including Rocky Mountain spotted fever, typhus fever, and scrub typhus. Rickettsia are transmitted to humans through the bites of infected arthropods, such as ticks, fleas, and lice. Once inside a host cell, Rickettsia manipulate the host cell's cytoskeleton and membrane-trafficking machinery to gain entry and replicate within the host cell's cytoplasm. They can cause significant damage to the endothelial cells that line blood vessels, leading to vasculitis, tissue necrosis, and potentially fatal outcomes if not promptly diagnosed and treated with appropriate antibiotics.
In the context of medicine and biology, symbiosis is a type of close and long-term biological interaction between two different biological organisms. Generally, one organism, called the symbiont, lives inside or on another organism, called the host. This interaction can be mutually beneficial (mutualistic), harmful to the host organism (parasitic), or have no effect on either organism (commensal).
Examples of mutualistic symbiotic relationships in humans include the bacteria that live in our gut and help us digest food, as well as the algae that live inside corals and provide them with nutrients. Parasitic symbioses, on the other hand, involve organisms like viruses or parasitic worms that live inside a host and cause harm to it.
It's worth noting that while the term "symbiosis" is often used in popular culture to refer to any close relationship between two organisms, in scientific contexts it has a more specific meaning related to long-term biological interactions.
Phylogeny is the evolutionary history and relationship among biological entities, such as species or genes, based on their shared characteristics. In other words, it refers to the branching pattern of evolution that shows how various organisms have descended from a common ancestor over time. Phylogenetic analysis involves constructing a tree-like diagram called a phylogenetic tree, which depicts the inferred evolutionary relationships among organisms or genes based on molecular sequence data or other types of characters. This information is crucial for understanding the diversity and distribution of life on Earth, as well as for studying the emergence and spread of diseases.
Ribosomal RNA (rRNA) is a type of RNA that combines with proteins to form ribosomes, which are complex structures inside cells where protein synthesis occurs. The "16S" refers to the sedimentation coefficient of the rRNA molecule, which is a measure of its size and shape. In particular, 16S rRNA is a component of the smaller subunit of the prokaryotic ribosome (found in bacteria and archaea), and is often used as a molecular marker for identifying and classifying these organisms due to its relative stability and conservation among species. The sequence of 16S rRNA can be compared across different species to determine their evolutionary relationships and taxonomic positions.
Wolbachia is a genus of intracellular bacteria that naturally infects a wide variety of arthropods (insects, spiders, mites) and filarial nematodes (roundworms). These bacteria are transmitted vertically from mother to offspring, often through the cytoplasm of eggs. Wolbachia can manipulate the reproductive biology of their hosts in various ways, such as feminization, parthenogenesis, male killing, and cytoplasmic incompatibility, which favor the spread and maintenance of the bacteria within host populations. The interactions between Wolbachia and their hosts have implications for insect pest management, disease transmission, and evolutionary biology.
'Anopheles' is a genus of mosquitoes that are known for their role in transmitting malaria parasites to humans. These mosquitoes have a distinctive resting posture, with their abdomens raised and heads down, and they typically feed on human hosts at night. Only female Anopheles mosquitoes transmit the malaria parasite, as they require blood meals to lay eggs.
There are over 400 species of Anopheles mosquitoes worldwide, but only about 30-40 of these are considered significant vectors of human malaria. The distribution and behavior of these mosquitoes can vary widely depending on the specific species and geographic location.
Preventing and controlling the spread of malaria involves a variety of strategies, including the use of insecticide-treated bed nets, indoor residual spraying, antimalarial drugs, and vaccines. Public health efforts to reduce the burden of malaria have made significant progress in recent decades, but the disease remains a major global health challenge, particularly in sub-Saharan Africa.
Southeast Asia is a geographical region that consists of the countries that are located at the southeastern part of the Asian continent. The definition of which countries comprise Southeast Asia may vary, but it generally includes the following 11 countries:
* Brunei
* Cambodia
* East Timor (Timor-Leste)
* Indonesia
* Laos
* Malaysia
* Myanmar (Burma)
* Philippines
* Singapore
* Thailand
* Vietnam
Southeast Asia is known for its rich cultural diversity, with influences from Hinduism, Buddhism, Islam, and Christianity. The region is also home to a diverse range of ecosystems, including rainforests, coral reefs, and mountain ranges. In recent years, Southeast Asia has experienced significant economic growth and development, but the region still faces challenges related to poverty, political instability, and environmental degradation.
Malaria is not a medical definition itself, but it is a disease caused by parasites that are transmitted to people through the bites of infected female Anopheles mosquitoes. Here's a simple definition:
Malaria: A mosquito-borne infectious disease caused by Plasmodium parasites, characterized by cycles of fever, chills, and anemia. It can be fatal if not promptly diagnosed and treated. The five Plasmodium species known to cause malaria in humans are P. falciparum, P. vivax, P. ovale, P. malariae, and P. knowlesi.
'Anopheles gambiae' is a species of mosquito that is a major vector for the transmission of malaria. The female Anopheles gambiae mosquito bites primarily during the nighttime hours and preferentially feeds on human blood, which allows it to transmit the Plasmodium parasite that causes malaria. This species is widely distributed throughout much of Africa and is responsible for transmitting a significant proportion of the world's malaria cases.
The Anopheles gambiae complex actually consists of several closely related species or forms, which can be difficult to distinguish based on morphological characteristics alone. However, advances in molecular techniques have allowed for more accurate identification and differentiation of these species. Understanding the biology and behavior of Anopheles gambiae is crucial for developing effective strategies to control malaria transmission.
Insect vectors are insects that transmit disease-causing pathogens (such as viruses, bacteria, parasites) from one host to another. They do this while feeding on the host's blood or tissues. The insects themselves are not infected by the pathogen but act as mechanical carriers that pass it on during their bite. Examples of diseases spread by insect vectors include malaria (transmitted by mosquitoes), Lyme disease (transmitted by ticks), and plague (transmitted by fleas). Proper prevention measures, such as using insect repellent and reducing standing water where mosquitoes breed, can help reduce the risk of contracting these diseases.