Transmission potential of the human head louse, Pediculus capitis (Anoplura: Pediculidae).

BACKGROUND: Millions of people are infested by head lice every year. However, louse transfer between hosts is not well-understood. Our goals were to determine: (1) which stages were most likely to disperse and why, (2) the likelihood of fomites transmission, and (3) if host blood gender affects louse development. METHODS: Various life stages of lice at differing densities were permitted to cross over a 15-cm hair bridge placed between two artificial blood-feeding arenas. Louse transfer caused by hot air movements, combing, toweling, and passive transfer to fabric was investigated. The ability of lice to oviposit on different foreign substrates and the hatching potential of eggs intermittently incubated for 8 h/night on a host were likewise investigated. Louse in vitro development following feeding on human female or male donor blood was compared. RESULTS: Adult lice were the most likely to disperse. Neither population density nor hunger significantly affected dispersal tendencies. Lice were dislodged by air movement, combs and towels, and passively transferred to fabric within 5 min. Females oviposited on a variety of substrates and 59% of eggs incubated for 8 h/night hatched after 14-16 days. There was no survivorship difference between lice artificially fed on female vs. male blood. CONCLUSIONS: Adult lice are the most mobile, indicating that they are most likely to initiate new infestations. Although head-to-head contact may be the primary route of transmission, less direct routes involving fomites may play a role and need further evaluation. Blood-borne factors do not appear to cause any gender-biased host preference.

Clinical and hematological findings on "Degnala", a disease of buffalo in Eastern Nepal.

A buffalo disease, called "Degnala", causing lameness, edema, gangrenous ulceration of hooves or tail, emaciation, recumbency and eventual death, occurs in Eastern Nepal. Clinical examinations manifested lice eggs on hairs, bradycardia, hypothermia, dehydration, exanthema and icterus. Hematologically, increase of band neutrophil, giant platelet, hypoalbuminemia and hyperglobulinemia were characteristics. Microscopically, dark blue tiny particles were seen on red blood cell (RBC) after Giemsa staining. Administration of tetracycline at an early stage of the disease was effective.

Linognathus vituli (Anoplura: Linognathidae): population growth, dispersal and development of humoral immune responses in nai;ve calves following induced infestations.

Growth of Linognathus vituli populations following establishment at a point source was followed for 16 weeks on eight louse-naïve Holstein calves. Dispersal of lice from the point of infestation (withers) was monitored by examination of known louse predilection sights. Mean louse indices increased during the initial weeks reaching maximum mean values at 8 weeks post-infestation (p.i.). Subsequently, mean indices decreased, reaching a plateau that persisted through weeks 14 and 15 p.i. There was little movement away from the withers until 5 weeks p.i. Subsequently, numbers of lice on the withers declined, while increasing at sites on the head. A few lice were noted on the dewlap and topline sites. Host antibody responses to crude nymph antigens, measured by enzyme-linked immunosorbent assay (ELISA), were generally evident within 2-4 weeks of infestation. Examination of individual host data showed louse populations could be categorized relative to the mean population size for the group. Two animals were considered 'chronic', having louse populations that persisted throughout the study and whose louse indices were >150% of the group mean. Two animals were classified as 'resistant' having lice present for only a portion of the study and whose louse indices <40% of the group mean. The remaining animals had louse indices between 62 and 137% of the group mean. Antibody profiles of the individuals were not as clearly categorized, although the 'resistant' animals were only positive for short periods of time, roughly corresponding to the time when lice were observed.

Short communication serum copper, zinc, and calcium concentrations in lice-infested sheep.

The purpose of this study was to investigate changes in serum concentration of copper, zinc, and calcium in sheep naturally infested with lice (Bovicola caprae, Linognathus africanus, Linognatus ovillus, and Linognattus pedalis). Twenty sheep naturally infested with lice and 20 healthy sheep were used as subjects. Blood samples were collected from the sheep before and 8 and 15 d after treatment with Avermectin, a veterinary antiparasitic drug. The samples were analyzed for their serum copper, zinc, and calcium concentrations by atomic absorption spectrometry. The concentrations of these elements in the infested animals were lower than in the healthy controls, mainly because the general condition of the affected sheep was poor. When the infested animals were treated with an ectoparasitic drug, the serum levels of the studied elements rose to normal ranges while the health of the animals improved.

Isolation, amplification, and sequencing of human mitochondrial DNA obtained from human crab louse, Pthirus pubis (L.), blood meals.

The ability to identify individual human hosts based on analyses of blood recovered from the digestive tract of hematophagous arthropods has been a long-term pursuit in both medical and forensic entomology. Blood meal individualization techniques can bring important advancements to studies of vector-borne disease epidemiology. Forensically, these analyses may aid in assailant identification in violent crime cases where blood-feeding insects or their excreta are recovered from victims or at crime scenes. Successful isolation, amplification, and sequencing of human mitochondrial DNA obtained from adult human crab lice fed on human volunteers are reported. Adult lice were removed from recruited volunteers frequenting inner city health clinics. Live lice were killed by freezing and subsequently air dried at ambient temperature. A saliva sample was obtained from each volunteer and served as a DNA reference sample. Volunteers were afforded free, approved pediculosis treatment. Individual lice were subsequently processed using procedures developed for the extraction of mitochondrial DNA from human hair, teeth, and bone. The resulting DNA was amplified by the polymerase chain reaction and sequenced. Our results point to valuable avenues for future entomological research.

Abnormal distribution of the histocompatibility antigens (HLA) in lousy patients.

The histocompatibility antigens have important functions in the development of the immune response, in the development of immunologic tolerance and in the resistance and susceptibility to diseases. In the present study, the frequency of the human leucocytic antigens (HLA) were studied in 31 lousy children with Pediculus h. capitis (head lice) and 14 adults with Phthirus pubis (pubic lice) to evaluate the immune response in their pathogenesis. The patients (children and adults) were parasite-free as indicated by urine, stool and blood analysis and clinical examination. A significant increase was found between HLA-A11 and, -B5 and lousy children with P. h. capitis and between HLA,-A11, -B5 and -B27 and lousy adults with P. pubis. The association between HLA antigens and parasitic infection was discussed.

[Lindane]. / Lindan.

In Europe and in the US ectoparasitic diseases are increasingly diagnosed in all classes of society. Modern means of transportation promote the spreading from endemic areas into new regions and therefore questions of therapy are becoming increasingly important. A series of preparations in various galenic formulations and in various concentrations are available to treat the ectoparasitic diseases. Due to reports on Lindane poisonings the clinical use of Lindane preparations for the treatment of scabies and pediculosis has become somewhat controversial. In this article we review older and more recent data on pharmacology, pharmacokinetics and toxicology of gamma-1,2,3,4,5,6-Hexachlorcyclohexan [Lindane]. It is pointed out that in the USA Lindane is offered in 1% preparations whereas in the German speaking Europe only 0.3% preparations are available. This latter concentration is considered as sufficient to treat the ectoparasitosis. Furthermore the use of this remedy and aspects of Lindane resistance are discussed. It is concluded that only through additional in depth education of the patients and their folks successful treatment is possible and intoxication can be prevented.

Basophil leucocytes in responses to parasitic infection and some other stimuli in sheep.

Basophil leucocytes are a significant component of the infiltrating cells in a variety of tissue reactions in guinea pigs. However, little is known about the participation of basophils in similar reactions in most other animal species. The circulating blood, skin and small intestinal mucosa of sheep were examined after they had received stimuli known to elicit basophil-rich responses in guinea pigs but relatively few basophils were found.

Ectoparasite impacts on Gerbillus andersoni allenbyi under natural conditions.

To assess ectoparasite impact on individuals and populations of Gerbillus andersoni allenbyi under natural conditions, I addressed the following questions. Do ectoparasites affect their host fitness and, if so, how? Do ectoparasites affect host population level? Does this parasite-host interaction support the traditional concept of parasite evolution towards avirulence? For this purpose, host infestation, infection, survival, haematological indices, and physical condition were recorded. A field experiment which included manipulating host infestation while recording host survival was conducted to determine the causal relations between these variables. G. a. allenbyi was infested by 2 fleas (Synosternus cleopatrae and Stenoponia tripectinata), 5 mesostigmatid mites (Androlaelaps centrocarpus, A. hirsti, A. insculptus, A. marshalli and Hirstionyssus carticulatus), 1 tick (Rhipicephalus sanguineus), and 1 louse (polyplax gerbilli). Ectoparasite burden significantly reduced host survival and red blood cell indices (red cell concentration, haemoglobin concentration and haematocrit). Ectoparasite burden did not significantly affect white blood cell concentration. Gerbils were not infected by haemoparasites or gut helminths which potentially could cause anaemia. The causal relationship between S. cleopatrae burden and host survival was established by manipulation of host infestation. Both ectoparasite removal and initial level of infestation significantly affected host survival. Ectoparasites that caused anaemia were not associated with host physical condition (PC), measured as weight/length3. None of the red blood cell indices was correlated with host PC. These results suggest both that host PC was not affected by ectoparasite burden and that exsanguination leading to anaemia was the main effect of the ectoparasites. Ectoparasite pressure on the host population (based on the ectoparasite effects as estimated by statistical models, combined with dispersion of the infestation within the host population) changed seasonally and was greatest when host density was the highest. A large segment of the gerbil population was affected by ectoparasites during the entire year. An explanation for the evolution of parasite virulence, contrasting parasites that evolve towards increased virulence with parasites that evolve towards avirulence is presented. This classification is primarily based on whether parasite impact is equated with a higher efficiency of host exploitation, or whether it is a 'side effect' of parasite biology.

Effects of low levels of lice and internal nematodes on weight gain and blood parameters in calves in central Texas.

The effects of low levels of both biting and sucking lice, a mixed population of nematodes, and a combination of all these parasites were evaluated in calves held in a barn with no environmental controls in central Texas. Observations at 122 sites on each animal for 16 wk consecutively in 1987 revealed that the largest numbers of all louse species [Haematopinus eurysternus (Nitzsch). Linognathus vituli (L.), and Bovicola bovis (L.)] occurred 3-7 wk after infestation. In 1988 L. vituli populations decreased rapidly after the 3rd wk and B. bovis remained fairly constant for 20 wk consecutively. Average nematode egg counts increased to approximately 300 eggs per gram of feces in 1987 and approximately 600 eggs per gram of feces in 1988. The nematodes Ostertagia ostertagia, Haemonchus placei, Oesophagostomum radiatum, Cooperia spp., and Trichostrongylus spp. were present at the end of the study in both years as determined by necropsy. No significant differences in erythrocyte count, mean cell volume, hematocrit, hemoglobin concentration, leukocyte counts, or serum albumin concentration were detected. However, significant increases in total serum protein concentration and serum globulin levels in calves harboring both groups of parasites were observed. Mean weight gain in calves infested with lice and nematodes was 11.4 and 10 kg less than that of uninfested controls during 16 wk in 1987 and 20 wk in 1988, respectively.

Blood parameters and turnover data in calves infested with lice.

Erythrokinetic and plasma protein turnover studies using 51Cr-red cells, 59Fe-transferrin and 125I-albumin, were carried out on young Ayrshire calves naturally infested with the long-nosed sucking louse Linognathus vituli. Throughout the trial none of the animals lost their appetite. Liveweight gain was greater in the uninfested animals but not significantly so. The infestation did not cause the animals to become anaemic, but plasma iron turnover rates were decreased and there was a significant increase in the red cell survival time. The circulating volumes of red cells and plasma were not significantly affected and the fractional catabolic rate of albumin was not markedly altered. At the end of the trial the mean red blood cell and mean total blood content of one louse was evaluated at 0.157 microliters and 0.443 microliters respectively, using 51Cr, and 0.120 microliters and 0.350 microliters respectively, using 59Fe. Using 125I the mean albumin content of one louse was 98.4 micrograms.

Influence of hog lice, Haematopinus suis, on blood components, behavior, weight gain and feed efficiency of pigs.

Blood components, behavior, weight gain and feed efficiency were studied in 40 weaner pigs infested with lice and 40 left uninfested (controls). Packed cell volumes and concentrations of hemoglobin, serum proteins, leukocytes, serum globulins, and serum albumins increased significantly in both groups. Eosinophil concentrations increased and neutrophil concentrations decreased in the infested group but not in the controls. There was a significant increase in erythrocyte concentrations in the control group while the infested group's erythrocyte concentrations decreased at the middle of the experiment. Blood of infested and uninfested pigs showed no significant differences from pre-infestation values in sedimentation rates and concentrations of fibrinogen, basophils, and monocytes. Control pigs spent more time at feeders and more time active while not at feeders. Nevertheless, average daily gains (ADG) and feed efficiencies (FE) of the two groups were not significantly different. When ADG and FE were grouped by severity of Haematopinus suis infestation, pigs with more H. suis had higher ADG and better FE than pigs with fewer or no lice. The results suggest that a decrease in activity by infested pigs allows them to save energy which is then available for growth.

Chlorpyrifos for control of the short-nosed cattle louse, Haematopinus eurysternus (Nitzsch) (Anoplura, Haematopinidae) during winter.

Two groups (A and C) of range cows were treated in February with chlorpyrifos (16 mL Dursban 44/cow) for the control of heavy infestations of the short-nosed cattle louse. Group A was treated in 1977 and group C in 1979 and each treated group was compared with a separate untreated group. Some of the treated cows were identified as carriers of louse infestation (subgroups A1 and C1), while others were noncarriers (subgroups A2 and C2). The maximum level of reduction in louse populations was 99% at week 4 posttreatment in subgroup A1, 99% from weeks 2-16 posttreatment in subgroup A2, 92% at week 3 posttreatment in subgroup C1 and 100% at weeks 15-17 in subgroup C2. Clinically, the treated cows, which were anemic at the time of treatment, recovered from anemia during the posttreatment period of 25 weeks for group A and 17 weeks for group C. Remission of anemia also occurred in the two untreated groups, possibly because of natural summer decline in louse population. The treatment had no effect on the whole blood cholinesterase of the cows and the treated cows showed no signs of organophosphorous toxicity.