Seasonal studies on commensal rats and their ectoparasites in a rural area of Egypt: the relationship of ectoparasites to the species, locality, and relative abundance of the host.

The present study was carried out in 3 villages, namely Kafr Ayoub Soliman, Kafr Ibrahim El-Aidi, and El-Sa'adat, Sharqiya Governorate, Egypt. A total of 519 rats was collected from the 3 study sites: 46.6% Rattus rattus, and 53.4% Rattus norvegicus. A total of 20,643 ectoparasites was recovered from R. rattus: 33.3% mites, 33.8% fleas, and 32.9% lice. From R. norvegicus a total of 40,997 ectoparasites was recovered: 28.9% mites, 31% fleas, and 40.1% lice. Three common mite species were recovered from both rat hosts, i.e., Ornithonyssus bacoti, Radfordia ensifera, and Laelaps nuttalli. Three common flea species were also recovered from both rat hosts, i.e., Echidnophaga gallinacea, Leptopsylla segnis, and Xenopsylla cheopis. Polyplax spinulosa was the only dominant louse species that infested both rat hosts. Rats did not show a definite breeding season, and the seasonal rat indices were generally low in different study sites. There were no significant differences between the prevalence of each of mites, fleas, and lice in both rat species. The total general indices of mites and fleas, on the other hand, was significantly higher in R. norvegicus. The general index of X. cheopis was high and ranged between 5.9 in R. rattus and 14.5 in R. norvegicus. Season-related changes were observed in the general index of each of L. segnis infesting both rat species and R. ensifera and O. bacoti infesting R. norvegicus. The prevalence and general indices of some ectoparasites showed differences related to the locality of their rat hosts. Seasonal changes in the general indices of some ectoparasites paralleled seasonal changes in the relative abundance of their rat hosts.

Fine structure of the synganglion of unfed female Rhipicephalus (Rhipicephalus) sanguineus (Latreille) (Ixodoidea: Ixodidae).

The synganglion of unfed female Rhipicephalus (Rhipicephalus) sanguineus (Latreille) is enclosed within a well defined neural lamella underlined by the perineurium. No organelles were observed in the neural lamella, whereas axons containing neurosecretory vesicles, tracheal elements and glycogen deposits are visible in the perineurium. Below the perineurium, a cortical layer of nervous and non-nervous elements surrounds an inner neuropile, the latter is enclosed by a thin subperineurial layer. The neuropile is formed of nerve fibers containing neurotubules.

Genital system structure of unfed female Rhipicephalus (Rhipicephalus) sanguineus (Latreille) (Ixodoidea: Ixodidae).

The reproductive system of female Rhipicephalus sanguineus consists of a single ovary, paired oviducts fusing into a single common oviduct, connecting tube, the vagina that in turn divides into cervical and vestibular regions, a wide receptaculum seminis and tubular accessory glands that open into the vagina between the cervical and vestibular regions. The histological structure of each part of the female reproductive system is described. The fine structure of the ovary, connecting tube and accessory glands is also provided in this study.

Effect of sex, size, and age of commensal rat hosts on the infestation parameters of their ectoparasites in a rural area of Egypt.

The present study was carried out in the Bilbeis area, Sharqiya Governorate, Egypt. A total of 127 male and 115 female black rats Rattus rattus and 124 male and 153 female Norway rats R. norvegicus was collected during the study period. A total of 20,643 and 40,997 ectoparasites was recovered from R. rattus and R. norvegicus, respectively. Three common mite species were recovered from both rat hosts: Ornithonyssus bacoti, Radfordia ensifera, and Laelaps nuttalli. Three common flea species were also recovered from both rat hosts: Echidnophaga gallinacea, Leptopsylla segnis, and Xenopsylla cheopis. Polyplax spinulosa was the only louse species that infested both rat hosts. Rats that lived more than 12 mo formed about 24 and 14% of the populations of the black and Norway rats, respectively. The prevalences and general indices of many ectoparasites were significantly higher on males than on females of both rat hosts. Seasonal differences in prevalences and general indices of many ectoparasites were recorded between the 2 sexes of both rat species. Prevalences and general indices of most ectoparasites on both rat species showed a tendency to increase with increasing size and age of rat hosts. The type and degree of correlation between prevalences and general indices on the one hand and each of body size and age on the other hand differed among the species of ectoparasites.

Effects of permethrin on the salivary glands and neuroendocrine organs of unfed female Hyalomma (Hyalomma) dromedarii (Ixodoidea: Ixodidae).

Permethrin-impregnated fabric has been shown to be an effective repellent against various tick species. However, some tick species are not repelled by this chemical. In Hyalomma dromedarii (Koch), permethrin exposure is reported to actually enhance the tick's attachment behavior. This study evaluated the histological effects of permethrin exposure on the salivary glands and neuroendocrine organs of unfed, virgin H. dromedarii ticks of uniform age. Three fabric treatments consisting of unwashed-untreated (control), washed after treatment (0.125 mg [AI] / cm2) and unwashed-treated were used after 5- and 10-min exposure times for unfed, unmated females. For all of the organs examined, the cellular structure of treated ticks differed from controls as evidenced by increases in cellular activity, as well as significant increases in the size of the cells of the organs under study (P < 0.05). These data conclusively demonstrate that an unexpected enhanced attachment response observed in this tick species after permethrin exposure is the direct result of increased neurosecretory and salivary gland activity induced by that exposure.

Peritonitis in Patients on CAPD at King Khalid University Hospital: Less Infection-rate with More Center-experience.

Continuous ambulatory peritoneal dialysis (CAPD) was started at the King Khalid University Hospital in 1986. Peritonitis remains the most significant complication of the procedure. Earlier rates of peritonitis were high, but after gaining sufficient experience, the rates are declining. To evaluate the change in peritonitis trend, 55 new patients who were recruited to our CAPD program between the periods October 1993-October 1996 were analyzed for the development of peritonitis on annual basis. There were 37 (67%) males and 18 (33%) females with a mean age of 43.3 years (range 12-72 years). A total of 34 episodes of peritonitis were recorded with a rate of 1.5 episode/patients year in 1993, 0.5 episode/patient year in 1994 and 0.8 in 1995. only 40% of episodes showed positive cultures whereas 60% remained culture-negative despite use of recommended modified culture techniques. Organisms causing peritonitis included staphylococcus eipdermides (6.7%), E. coli (3.3%), Streptococcus fecalis (3.3%) and pseudomonas (6.7%). Out of 34 episodes of peritonitis, 29 (85.3%) showed response to treatment and five episodes could only be treated after removal of catheter. Of the 29 episodes that responded to treatment, three relapsed and one had recurrent infection . However, all were successfully treated though one responded only after removal of catheter. Thus, a total of six catheters (20%) necessitated removal and replacement. In spite of high diabetic patients population in our series (27.2%) only one died of peritonitis related sepsis and another died of myocardial infarction after clearing the infection. Thus mortality remains low in spite of potential risk. Although we still use straight system CAPD rather than Y system peritonitis rates have declined considerable and we hope that the procedure will gain more acceptability amongst patients with ESRD in Saudi Arabia.

Effect of 25-azacholestane on Argas (Argas) hermanni (Ixodoidea:Argasidae).

Unfed and fed nymphal Argas hermanni Audouin were treated topically with 1, 5, 10, 15, and 20 micrograms of 25-azacholestane. The azasteroid did not inhibit feeding but had a dose-related lethal effect on unfed nymphs. Generally, it had little effect on nymphs treated after feeding. The 10-micrograms dose reduced the premolting period of nymphs treated before feeding. Some adults emerging from the 5- to 20-micrograms dosage groups that had been treated before feeding failed to shed their exuvia and others also had deformed legs. Greater numbers of adult females emerged from nymphs treated before feeding. The preoviposition period was almost the same in control females and of female mates, with males emerging from treated nymphs. Females from nymphs treated before feeding have a prolonged preoviposition period. Fecundity was reduced when males were treated with 10-20 micrograms as unfed nymphs. Egg hatch was reduced for females treated with 15 and 20 micrograms as fed nymphs, females treated with 5 and 10 micrograms as unfed nymphs, and as progeny of males treated with 10 micrograms as unfed nymphs. Results suggest possible interference with juvenile hormone titer in treated ticks.

Biochemical changes in the coxal organ proper and accessory glands of female Ornithodoros (Ornithodoros) savignyi at different physiological conditions.

Changes in the total protein, DNA, RNA, lipid and phospholipid concentrations in the coxal organ proper and accessory glands of Ornithodoros (Ornithodoros) savignyi (Audouin) were studied. There was an increase in the total protein, DNA, RNA, lipid and phospholipid content of the coxal organ proper in the female upto 6-days after feeding, then the concentration decreased. Also, the content of protein, DNA, RNA, lipid and phospholipid in the coxal organ proper of the seventh nymphal instar were similar to unfed females. Accessory glands showed an increase in protein, DNA, RNA, lipid and phospholipid content that reached its maximum on day 8 after feeding in females, then decreased.

Changes in the salivary glands of female Hyalomma (Hyalomma) dromedarii during and after feeding.

The salivary glands in female H. dromedarii consists of three alveolar types, one agranular (type I) and two granular (type II and III). Five granule secreting cell types were identified according to their granular submicroscopic appearance. The structure and changes observed in type I alveoli before, during and after feeding suggest its role in ion and water transport from the haemolymph to the lumen during initial feeding. Secretory cells in salivary alveoli types II and III undergo substantial growth, differentiation and accumulation of secretory material during feeding and various rates of depletion directly after feeding. Attachment and limited feeding seems to provide a stimulus for synthesis of proteins, lipids and carbohydrates, whereas detachment from the host decreases the secretory competence of these alveoli causing its degeneration.

West Nile virus (Flaviviridae:Flavivirus) in experimentally infected Argas ticks (Acari:Argasidae).

To better define the possible role of argasid ticks in the epidemiology of West Nile virus, adult Argas arboreus, A. persicus, and A. hermanni were fed through a membrane on fetal bovine serum containing 10(5.5) 50% tissue culture infective doses (TCID50)/ml of West Nile virus. The virus was detected for three and four days after feeding in A. persicus and A. hermanni, respectively. The virus titers then decreased to undetectable levels in both species. When the infective dose was increased to 10(6.2), virus was detected until days 6 and 8, respectively. In A. arboreus, virus titers in whole tick homogenates reached a peak of 10(4.0) on day 4 postfeeding and remained constant at 10(3.0) after day 6 throughout the 20- or 50-day observation periods. Virus was detected by isolation, indirect fluorescent antibody, and histochemical techniques in the salivary glands, ovaries, synganglia, and coxal fluids. Infected ticks successfully transmitted virus to clean chickens on day 20 postfeeding. No evidence of transstadial transmission from nymph to adult was detected. Larvae from experimentally infected females successfully transmitted virus to clean chicks and virus was recovered from F1 larvae. Venereal transmission was not detected. Virus was present in coxal fluids secreted by infected females after infective meals. This study demonstrates West Nile virus infection in experimentally infected A. arboreus ticks and documents horizontal and vertical transmission in this species.

Nucleic acid levels in the developing ovaries of Hyalomma (Hyalomma) dromedarii (Acari: Ixodidae).

Protein and nucleic acid levels from the ovaries of Hyalomma dromedarii Koch were determined during different stages of oogenesis. The concentrations of total protein, DNA, and RNA increased during oogenesis, reflecting the rapid developmental changes taking place in this tissue. Peak protein and DNA levels were reached in the fully fed females, whereas RNA level peaked slightly earlier. Ribosomal RNA (rRNA) was found to be composed of 27.0s, 17.0s, and 4.1s particles. The ratio of 27.0s to 17.0s varied within the developing ovary, yet the 27.0s/4.1s ratio remained constant. The nucleotides of total RNA and rRNA were determined, and the ratio of purine/pyrimidine equaled approximately 1 and remained unchanged during oogenesis.

Biochemical changes in Hyalomma (Hyalomma) dromedarii (Acari: Ixodidae) embryos and effect of 20-hydroxyecdysone applied to the mother.

Changes in DNA, RNA, total lipids, phospholipids, and proteins and the activity of certain enzymes and pattern of their isozymes were studied in Hyalomma dromedarii Koch during embryogenesis. Total proteins fluctuated with a net increase (P less than 0.05) on day 20. Total lipids increased during the first half of embryogenesis and then declined with a net decrease to about 60% of the original level. Total phospholipids decreased to half this original level. DNA content increased greatly during cleavage, gastrulation, and organogeny and RNA increased during cleavage and blastula formation. Glucose-6-phosphate dehydrogenase (G6PDH) activity decreased (P less than 0.05), reaching 20% of its original level on day 12. Malic acid dehydrogenase (MDH) activity remained nearly unchanged throughout embryogenesis. Lactic acid dehydrogenase (LDH) activity increased greatly, with the highest level on day 14 with no further change. Acetylcholinesterase (AchE) activity increased greatly during the first 12 d, with no significant change thereafter. Acid (ACP) and alkaline (ALP) phosphatase activity increased during the first 12 d and declined returning to the original level on day 20. Seven AchE and 5 LDH isozymes were detected during different embryogenesis stages. Two MDH, 2 ACP, 1 ALP, and 2 G6PDH isozymes were detected throughout embryogenesis. Treating the mother with 20-hydroxyecdysone was associated with increases in protein and RNA contents and G6PDH and AchE activity and with decreases in ACP and ALP activity in the embryos.

Biochemical effects of juvenile hormone III on the tick, Argas (Persicargas) arboreus (Acari: Argasidae), during embryogenesis.

The biochemical effects of juvenile hormone III (JH III) on developing embryos from treated female Argas (Persicargas) arboreus Kaiser, Hoogstraal and Kohls were examined. Exogenous JH III resulted in a decrease in total proteins (P less than 0.001) only during the first 2 d of embryogenesis. There was no significant difference (P greater than 0.05) between RNA and DNA content in eggs from control and JH III-treated females. No significant difference (P greater than 0.05) was observed between control and JH III eggs in their lipid or phospholipid contents throughout embryogenesis. A total of 14-17 protein bands and 6-8 glycoprotein bands were separated by electrophoresis during embryogenesis of A. arboreus with some differences in mobility ratio between bands from control and JH III eggs. Differences in activity and isozyme patterns of malic acid, lactic acid, glucose 6-phosphate dehydrogenase, acid phosphatase, and alkaline phosphatase were not observed during embryogenesis of control and JH III-treated A. arboreus. Differences were observed in esterase activity.

Vaginal eversion in a bat tick, Argas (Chiropterargas) boueti Roubaud and Colas-Belcour (Acari: Argasidae).

Vaginal eversion was observed in Argas (Chiropteragas) boueti. During eversion, both cervical and vestibular parts of the vagina are fully everted so that the former is anteriorly oriented, whereas the latter occupies the posterior end of the everted organ. The histology of normal and everted vaginas is described and correlated with its functional and biological significance. Vaginal eversion most likely occurs while the tick is ovipositing and may be involved in the wax-coating process of eggs by Gene's organ.

Effect of 20-hydroxyecdysone on neurosecretory cell activity in female Hyalomma dromedarii synganglion (Acari: Ixodidae).

Twenty micrograms of 20-hydroxyecdysone (20-HE) were applied topically to nymphal Hyalomma dromedarii Koch on the day of detachment. In emerging adult females, some neurosecrtory cells (NSC) in certain synganglion centers exhibited changes in size and/or neurosecretory material (NSM) shape, distribution and/or quantity. These changes were compared with those normally occurring in untreated unfed, semifed virgin and mated, and engorged females. 20-HE effects included (a) accelerating the changes induced by mating and/or feeding in certain NSC, (b) reducing, to various extents, NSC response to mating and feeding, and (c) inducing changes in some NSC which do not normally exhibit any changes in untreated females. The results suggest that (a) most female NSC respond more or less similarly to indigenous 20-HE, (b) 20-HE may have a role as a positive feedback regulator for NSM synthesis and/or release by certain NSC, (c) the response to 20-HE may be primarily a function of NSC location in the synganglion, and/or (d) NSC considered to be of one type may actually belong to different cell types.

The subgenus Persicargas (Ixodoidea: Argasidae: Argas): A. (P.) arboreus central nervous system anatomy and histology.

The anatomy and histology of the adult Argas (Persicargas) arboreus central nervous system are described and compared with these properties in other ticks. The single, integrated, central nerve mass (CNM) is formed by a fused supra-esophageal part (protocerebrum, cheliceral ganglia, palpal ganglia, and stomodeal pons) and a subesophageal part (4 pairs of pedal ganglia and the complex opisthosomatic ganglion). Single peripheral nerves (pharyngeal and recurrent) and paired peripheral nerves (compound protocerebral, cheliceral, palpal, pedal and opisthosomatic) extend from the CNM to body organs and appendages. Optic nerves, described in other Argas species, are not found in A. (P.) arboreus. Histologically, the CNM is enclosed by a thin-walled periganglionic blood sinus and invested by a collagenous neural lamella followed by a perineurial layer composed of glial cells and containing fine reticular spaces, a cortical layer of association, motor and neurosecretory cell bodies and glial cells, and inner neuropile regions of fiber tracts forming 5 horizontal levels of connectives and commissures.