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Murine typhus in Kuwait in 1978.

Murine typhus occurred in 254 individuals in Kuwait between April and August 1978; 81% of patients were aged between 15 and 44 years, and 63% were male. The highest attack rate occurred among people in the lowest socioeconomic class. The outbreak coincided with a period of high rat and flea density. A study of the first 104 cases suggested that infection was acquired in the home, but a case - control study revealed no significant differences between patients and control subjects in terms of exposure to rats or domestic animals, and other factors. This suggests that murine typhus is hyperendemic rather than epidemic in Kuwait. The disease is being controlled through reduction of both flea and rat populations. Murine typhus may be much more common in many areas than is generally realized, and its status should be re-evaluated regularly in all known and potential foci.

Adolescent↗

Complete mitochondrial DNA sequence of a tadpole shrimp (Triops cancriformis) and analysis of museum samples.

The complete mitochondrial DNA (mtNDA) of the tadpole shrimp Triops cancriformis was sequenced. The sequence consisted of 15,101 bp with an A+T content of 69%. Its gene arrangement was identical with those sequences of the water flea (Daphnia pulex) and giant tiger prawn (Penaeus monodon), whereas it differed from that of the brine shrimp (Artemia franciscana) in the arrangement of its genes for tRNAs. Phylogenetic analysis revealed T. cancriformis to be more closely related to the water flea than to the brine shrimp and giant tiger prawn. We also compared the 16S rRNA sequences of five formalin-fixed tadpole shrimps that had been collected in five different locations and stored in a museum. The sequence divergence was in the range of 0-1.51%, suggesting that those samples were closely related to each other.

Animals↗

The aesthetasc concept: structural variations of putative olfactory receptor cell complexes in Crustacea.

The structure of the aesthetascs has been investigated in the prawn Macrobrachium rosenbergii (larvae and juveniles), the opossum shrimp Neomysis integer, the euphausid Meganyctiphanes, and in the water-fleas Daphnia magna and D. longispina. The aesthetascs, that are thought to represent olfactory receptors, exhibit a considerable structural variation, ranging from the well known aesthetascs of higher crustaceans (lobster, crab, crayfish) to the corresponding sensilla found in the water-fleas and the males of opossum shrimps. The two following morphological characteristics of the aesthetascs are thought to indicate an olfactory function: the shape of the cuticular hair that is long and essentially hose-shaped, and the thin, loosely arranged cuticle of at least the outer part of the cuticular hair. The presence of other structural elements such as sensory cells, cilia, and enveloping cells are vital for the olfactory function, but the development is variable, which makes their use in the morphological definition of aesthetascs problematic.

Animals↗

Family pesticide use and childhood brain cancer.

The relationship between family pesticide use and childhood brain cancer was examined in a case-control study. Telephone interviews were conducted from June 1989 through March 1990 with the natural mothers of 45 childhood brain cancer cases, 85 friend controls, and 108 cancer controls. In comparisons to friend controls, significant positive associations were observed for use of pesticides to control nuisance pests in the home, no-pest-strips in the home, pesticides to control termites, Kwell shampoo, flea collars on pets, diazinon in the garden or orchard, and herbicides to control weeds in the yard. In comparisons to cancer controls, significant positive associations were observed for use of pesticide bombs in the home, pesticides to control termites, flea collars on pets, insecticides in the garden or orchard, carbaryl in the garden or orchard, and herbicides to control weeds in the yard. In general, positive associations in comparisons to one control group were supported by elevated odds ratios in comparisons to the other control group. Several potentially important associations were identified in this study. However, small sample sizes, potential recall bias, multiple comparisons, and lack of detailed exposure verification require further research to confirm these findings.

Brain Neoplasms↗

Bubonic plague: a molecular genetic case history of the emergence of an infectious disease.

Yersinia pestis, the bacterial agent of bubonic plague, is transmitted primarily by fleas and has been responsible for devastating epidemics throughout history. Y. pseudotuberculosis is a food- and water-borne pathogen that causes a much more benign enteric disease in humans. Despite these profoundly different pathogenesis strategies, the two bacteria are very closely related phylogenetically. Thus, identifying the specific genetic differences between them should provide an instructive case study in the evolution of microbial pathogenicity. Some key pathogenesis-related genes of Y. pestis and Y. pseudotuberculosis that have been described to date are compared in this review. Factors that potentiate plague transmission as well as disease are discussed, since dependence on the blood-sucking flea for transmission likely fueled the selection of virulent Y. pestis strains able to produce a high-density bacteremia. Retracing the evolutionary steps between these two Yersinia species may ultimately furnish a historical model for the sudden emergence of new human disease agents.

Animals↗

Two Brassica napus polygalacturonase inhibitory protein genes are expressed at different levels in response to biotic and abiotic stresses.

Plants encode a distinct set of polygalacturonase inhibitory proteins (PGIPs) that function to inhibit polygalacturonase enzymes produced by soft-rot fungal pathogens. We characterized two PGIP-encoding genes ( Bnpgip1 and Bnpgip2) from Brassica napus DH12075 (a double-haploid line derived from a cross between 'Crésor' and 'Westar'). The two proteins exhibit 67.4% identity at the amino acid level and contain 10 imperfect leucine-rich repeats. The pgip genes are present as a small multigene family in B. napus with at least four members. Bnpgip1 and Bnpgip2 are constitutively expressed in roots, stems, flower buds and open flowers. In mature leaf tissue, different levels of induction were observed in response to biotic and abiotic stresses. Bnpgip1 expression was highly responsive to flea beetle feeding and mechanical wounding, weakly responsive to Sclerotinia sclerotiorum infection and exposure to cold but not to dehydration. Conversely, Bnpgip2 expression was strongly induced by S. sclerotiorum infection and to a lesser degree by wounding but not by flea beetle feeding. Application of jasmonic acid to leaves induced both Bnpgip1 and Bnpgip2 gene expression; however, salicylic acid did not activate either gene. Taken together, these results suggest that separate pathways regulate Bnpgip1 and Bnpgip2, and that their roles in plant development or resistance to biotic and abiotic stress differ.

Amino Acid Sequence↗

Effects of orally administered chemotherapeutics (quinine, salinomycin) against Henneguya sp. Thelohán, 1892 (Myxozoa: Myxobolidae), a gill parasite in the tapir fish Gnathonemus petersii Günther, 1862 (Teleostei).

When given orally, quinine or salinomycin cause irreversible damage to the plasmodial developmental stages of Henneguya sp., a gill parasite in the tapir fish Gnathonemus petersii. Naturally infected tapir fish measured 75-169 mm in total length and their total weight ranged over 4.3-11.7 g. The fish bore 7-77 plasmodia in their gill arches. Medicinal food containing either quinine (5 g/1000 g food) or salinomycin (0.075 g/1000 g food) was given once a day to naturally infected fish in a food chain via water fleas ( Daphnia spp) for a period of 3, 6, or 9 days. From the monitored feeding of the tapir fish and weight determinations of the water fleas, it was calculated that gross uptake was 18.5 micro g/kg body weight fish daily for pure salinomycin and was 1.25 mg/kg body weight daily for quinine. After the end of the experiments, the fish were sacrificed and the plasmodia were carefully prepared from the gill arches and processed for transmission electron microscopy. As seen by ultrastructure investigations, for both substances the grade of damage in the parasites correlated positively with the period of application. When quinine was given for a 3-day period, the trophozoite ecto- and endoplasm exerted numerous vacuoles, caused by the drug, and the presporogonous and the pansporoblastic stages were malformed. Following a 6-day period, numerous abortive polar capsules were found in the trophozoite cytoplasm. To a large extent, the limiting membranes of the polaroblasts and valvogenic cells were destroyed. In addition, deep clefts between the polaroblasts, the valvogenic cells and between the two sporoblasts were observed. Following a 9-day treatment, all damage increased and, in addition, generative cells and two-cell stages were no longer detectable. As a first sign for the effects of salinomycin, following a 3-day treatment, a shrinking of the whole plasmodia occurred and the sutures in the pansporoblasts were enlarged. The polar capsules were malformed and the zonar structures of the polar filament were no longer detectable. The sporoplasmosomes were more electron-pale than those of the control samples. After a 9-day treatment, the pansporoblasts were completely destroyed. Under the experimental conditions chosen, both compounds were very well tolerated by the fishes.

Administration, Oral↗

Investigations on the biology, epidemiology, pathology and control of Tunga penetrans in Brazil: III. Cytokine levels in peripheral blood of infected humans.

Tungiasis is caused by penetration of the female jigger flea, Tunga penetrans, into the skin of its host. This parasitic skin disease is almost invariably associated with intense inflammation around embedded fleas, the underlying mechanisms being unknown. A study was undertaken to determine whether the inflammatory process can be attributed to immune activation induced by a biologically active foreign body. We determined the concentrations of Th1-mediated (IFN-gamma, TNF-alpha) and Th2-mediated (IL-4) cytokines in the sera of patients with tungiasis. The results were compared with those of controls infected with different helminths or exposed to soil-transmitted helminths. The results show that tungiasis causes a mixed Th1 and Th2 immune response, characterized by significantly increased concentrations of the pro-inflammatory cytokines IFN-gamma and TNF-alpha, with a slightly increased concentration of IL-4. The preponderance of the Th1 immune response was indicated by a significantly increased TNF-alpha/IL-4 ratio in patients with tungiasis, as compared with the control groups.

Adolescent↗

Molecular phylogeny of isolates of Ctenocephalides felis and related species based on analysis of ITS1, ITS2 and mitochondrial 16S rDNA sequences and random binding primers.

The phylogenetic relationships among 31 different flea isolates representing seven different species were studied by nucleotide sequence comparison of the internal transcribed spacer 1 (ITS1), internal transcribed spacer 2 (ITS2) and/or mitochondrial 16S ribosomal RNA gene (mt16S-rDNA) to examine the patterns of variation. Results show that all regions are useful in discriminating among flea species. In Ctenocephalides felis and Tunga penetrans, some differences in these gene regions occurred among different isolates within the same species. In the latter case, the differences are in the mt16S-rDNA region, with one isolate showing 48% divergence in nucleotide sequence. The taxonomic implications of this result are unclear at present. The gene regions revealed differences between C. felis isolates only after DNA sequencing the PCR products. Further differentiation among C. felis isolates was obtained using four different random binding primers (decamers) and primers for mammalian aldolase to amplify narrow differences in the genome. Using these primers we were able to discriminate between different C. felis isolates and determine that some of the genetic variation coincided with minor differences in response to the control agent imidacloprid. However, overall findings do not support the existence of subspecies of C. felis.

Animals↗

Morphological phylogeny of Geusibia Jordan, 1932 (Siphonaptera: Leptopsyllidae) and the host-parasite relationship with pikas.

Thirteen species of fleas of the genus Geusibia Jordan, 1932 were included in a cladistic analysis based on morphological characters. The results support Geusibia as a monophyletic group within Ctenophyllus Wagner, 1927 (sensu lato) and there are five diagnostic characters that distinguish Geusibia from related genera of Ctenophyllus (s. l). There is no evidence to support a subgeneric classification. We propose that G. ochotona Zhan, Cai & Wu, 1997 and G. lacertosa(Smit, 1975) are junior synonyms of G. torosa Jordan, 1932. After a reconciliation analysis, only two co-speciation events were found in the host-parasite association between Geusibia and pikas (Ochotona:Ochotonidae: Lagomorpha). Therefore, there are no co-evolutionary relationships between them, although a high host preference of Geusibiaspp. is recorded. The distribution and host selection of Geusibia, relative to host associations, are also discussed. Although most specimens of Geusibia are found on pikas, the host is not the definitive factor in the distribution of the genus. Some environmental factors and some host behaviors also determine the presence of Geusibia. Therefore, Geusibia is defined as a host-habitat-dependent flea.

Animals↗

The black death past and present. 1. Plague in the 1980s.

This paper considers firstly the epidemiology of plague in the 1980s. The largest number of cases occurred in Tanzania. Most cases were in children and young adults; in the USA the male:female ratio was about 2:1. Plague had a seasonal distribution. Almost all cases arose from bites of infected rodent fleas, and Rattus spp. were the most important reservoir hosts. Virulence is linked with the presence of a 45 MDa plasmid. The predominant clinical form of plague is bubonic, followed by septicaemic, meningitic and pneumonic. For treatment, streptomycin is the antibiotic of choice, with tetracycline and chloramphenicol as alternatives. Treatment given on the first 1-2 d of illness is highly effective, and resistance is not a problem. Rodent control, insecticide application, and avoidance of contact with rodents and their fleas remain the prime means of control. Plague vaccine is not in general use.

Animals↗

Comparative studies on ecotoxicology of synthetic detergents.

To predict the comparative toxicological response of synthetic detergents on aquatic ecosystems, the effects of various concentrations of neutralized alkyl benzene sulfonate were studied. The median tolerance limit at 48 hr, 95% confidence limit, slope function, presumable harmless concentration, and rate of survival of different species of aquatic fauna such as water fleas (Daphnia magna), mosquito larvae (Culex pipiens), slug worms (Tubifex rivulorum), snails (Lymnaea vulgaris), tadpoles (Rana cyanophlyctis), and fish fingerlings (Cirrhina mrigala) were followed at 0, 24, 48, 72, and 96 hr. Any effect on quality of the water was also tested after the addition of various concentrations of detergents. The results showed that water fleas are more susceptible to detergent toxicity than fish fingerlings, tadpoles, slug worms, snails, and mosquito larvae. Behavioral changes were also observed as an index for detergent toxicity. The relative toxicity of the detergents to various species is discussed in relation to selective ecotoxicological response.

Animals↗

Topics in pediatric dermatology.

Skin conditions of puppies and kittens are often infectious, such as ectoparasites or dermatophytosis. Hereditary and congenital skin problems are often detected at an early age. Young animals may be more prone to toxicity from medications, and labels should be read carefully for age limits. Husbandry factors, including nutrition, ectoparasites,temperature and humidity, cleaning products, and bedding, should be considered. Fleas are still a common problem despite recent improvements in flea control and can be debilitating in young animals because of blood loss.

Animals↗

Arthropods in dermatology.

Arthropods are important in medicine for a multitude of reasons. Their bites and stings may induce allergic reactions, ranging from annoying to life-threatening. Many arthropod products are also capable of inciting allergic responses in sensitized persons. In recent years, bites and stings have gained greater attention owing to increased concern about disease transmission. A common hypersensitivity response to arthropod bites, stings, and products is papular urticaria. This eruption occurs primarily in children, who eventually "outgrow" this disease, probably through desensitization after multiple arthropod exposures. Papular urticaria is most often caused by fleas or bedbugs, but virtually any arthropod is capable of inducing such a reaction. Two arthropod classes of medical importance are the Arachnida (spiders, scorpions, ticks, and mites) and the Insecta (lice, fleas, bedbugs, flies, bees, and ants). Animals in these two classes are probably responsible for more morbidity and mortality worldwide than are any other group of venomous creatures. In general, the diagnosis of arthropod bites and stings is dependent on maintenance of a high index of suspicion and familiarity with the arthropod fauna not only in one's region of practice, but also in the travel regions of one's patients. Learning objective At the completion of this learning activity, participants should be familiar with the clinical manifestations caused by a variety of arthropods as well as the treatment and possible sequelae of arthropod attacks.

Animals↗

Endosymbionts of Ctenocephalides felis felis (Siphonaptera: Pulicidae) obtained from dogs captured in Belo Horizonte, Minas Gerais, Brazil.

Specimens of fleas Ctenocephalides felis felis (1052 female symbol/448 male symbol), obtained from 150 dogs in Centro de Controle de Zoonoses de Belo Horizonte, Minas Gerais, Brazil, were dissected and examined for endosymbionts. Three protozoan, Nolleria pulicis, a gregarine (Actinocephalidae) and Leptomonas sp., together with one cestode, Dipylidium caninum were identified. Infections by N. pulicis and Leptomonas sp. occurred mainly in the warm-rainy period. The prevalence and distribution of these endosymbionts in fleas derived from Brazil and South America, and the their variation according to sex and season, are reported for the first time.

Animals↗

The random amplified polymorphic DNA (RAPD) assay to determine DNA alterations, repair and transgenerational effects in B(a)P exposed Daphnia magna.

The random amplified polymorphic DNA (RAPD) is a useful assay for the detection of genotoxin-induced DNA damage and mutations. In this study, we have further evaluated the potential of this assay to measure benzo(a)pyrene [B(a)P]-induced DNA changes, and repair (in kinetic experiments) as well as transgenerational effects in the water fleas, Daphnia magna. The organisms, which reproduce parthenogenetically, were exposed to 50 microg L(-1) B(a)P for 3 or 6 days and were allowed to recover in clean medium for 12 or 9 days, respectively. Qualitative and quantitative changes were observed in RAPD profiles generated not only from the B(a)P exposed Daphnia but also from previously treated organisms during the recovery experiments. The fact that some of the RAPD changes disappeared at the end of both recovery experiments suggested that the DNA effects were fully repaired or reversed. In addition, some of the B(a)P-induced RAPD alterations detected in parental D. magna were also observed in the offspring patterns. This suggested that DNA alterations that occurred in germ cells were probably transmitted to the next cohorts. The present study shows that the RAPD method can be useful to qualitatively assess the kinetics of DNA changes, repair and transgenerational effects and such effects could potentially be linked to survival and reproductive success at higher levels of biological organisation. In addition, the water fleas have efficient capabilities to repair or reverse B(a)P-induced DNA effects. Finally, unrepaired or misrepaired genetic damage induced by genotoxins such as B(a)P could be transmitted to next generations in these parthenogenetically reproducing organisms.

Animals↗

Tungiasis in rural Haiti: a community-based response.

Tungiasis is a disease endemic to poor communities in Latin America, the Caribbean and Africa. It is caused by the female flea, Tunga penetrans, which burrows into the skin of its host to feed while producing and extruding eggs. Consequent lesions may be painful and even crippling with damage ranging from mild erythema and swelling to necrosis. Superinfection of lesions can be serious and may result in auto-amputation or death from tetanus. We describe an outbreak of tungiasis in rural Haiti and a community-based intervention used to address it. Of 177 patients assessed, 132 (47 female, 85 male, 23 children) had tungiasis lesions. Forty-four patients had clinical signs of superinfection; 15 had ectopic lesions. Community health workers cleaned and disinfected patients' feet and any parts of the body with ectopic lesions, and then extracted fleas from existing lesions. Patients with superinfections were treated with appropriate antibiotics. Over 1000 pairs of shoes were distributed in the villages. Over 400 adults were given tetanus vaccinations during follow-up visits. Patients who had been treated reported feeling better and those who had received shoes indicated they had not developed new lesions. All superinfections were resolved. We concluded that community-based care can treat tungiasis effectively.

Adolescent↗

Preliminary observations on factors responsible for long persistence and continued outbreaks of plague in Lushoto district, Tanzania.

Human plague has been an important public health problem in Tanzania for over a century. Recorded outbreaks of the disease have been reported from various parts of Tanzania, including Iringa, Kagera, Singida, Mbulu, Arusha and Kilimanjaro since 1886. Since 1980 however, only Lushoto, Singida and Karatu districts have experienced outbreaks of the disease. Of these areas, Lushoto has disproportionately high incidences of the disease and this has persisted for nearly 17 years. Efforts to curb the disease through conventional methods, including control of vectors and reservoirs, chemotherapy and chemoprophylaxis, enforcement of sanitation improvement as well as health education, have been applied every year, but plague cases and deaths continue to occur in the area to date. During the period April 1980 to December 1996, a total of 6599 cases with 580 (8.8%) deaths were recorded. Biological factors, such as the presence of suitable rodent reservoirs, efficient flea vectors and plague bacillus, could be partly responsible for the long persistence and recurrence of the disease. Since such factors are also common in other plague foci where the disease has never been persistently recurrent, and where indigenous people are culturally different from those in Lushoto, it is assumed that socio-cultural factors play an important role as determinants of the disease in the latter district. This paper reports preliminary observations on socio-cultural, biological and environmental factors which are thought to be, at least partly, responsible for the long persistence and repeated outbreaks of plague in the district. These include traditional beliefs on the cause and health seeking behaviour for treatment of plague, sleeping and food storage habits, large populations of rodents and fleas, and status of the immediate environment.

Adult↗