Experimental skin lesions from larvae of the bot fly Dermatobia hominis

Skin biopsies from larvae of Rattus norvegicus, experimentally infested with Dermatobia hominis (Linnaeus Jr) (Diptera: Cuterebridae), were processed for histopathological studies. Two days after infestation, the first-stage larvae (L1) were located deep in the dermis, surrounded by an inflamed area infiltrated predominantly by neutrophils. On the fourth day a thin necrotic layer could be seen close to the larvae, surrounded by large numbers of neutrophils, lymphocytes, macrophages with a few eosinophils and mast cells. A small warble was formed after the fourth day, increasing in size until the seventh day, when the L1 moulted to the second-stage larva (L2). The inflammatory process continued with increasing numbers of neutrophils, macrophages, lymphocytes, eosinophils and mast cells invading the area, as well as the proliferation of fibroblasts and endothelial cells and the appearance of a few localized haemorrhages. After 18-20 days, the L2 moulted to the third-stage larva (L3), when a few plasma cells could be seen in the inflamed area. At 25-30 days there was a reduction in the necrotic layer, as well as in the number of neutrophils and lymphocytes, although large amounts of eosinophils, plasma cells, and collagen fibres were seen. The L3 usually left the host after 30 days. Two days later, the larval cavity was reduced, mast cells infiltrated the region and collagen fibre production were increased. After 7 days, an intense infiltration of plasma cells and scattered necrotic areas could be seen. A scar formed after 10 days. This study showed the laboratory rat to be a suitable model for studies of D. hominis infestation.     

Eosinophil and mast cell expression in host skin during larval development of the human bot fly Dermatobia hominis

Eosinophils and mast cells in the skin of Wistar rats (Rattus norvegicus) infested with Dermatobia hominis larvae were quantified and analysed. Eosinophils in parasitised skin increased markedly until 10 days post-infestation (dpi) and then decreased up to 28 dpi, close to the point at which third stage larvae (L3) emerged from the host. In ascending order, the highest numbers of eosinophils were seen in rats at 1, 4, 28, 20, 15 and 10 dpi, corresponding to the first, (1 and 4) third (20 and 28) and second (10 and 15) instars. Except for 1 dpi, eosinophil numbers were significantly higher than those seen in control animals. Mast cell numbers were highest in early infestation (4 dpi), followed by those at 20 dpi. In increasing order, numbers of mast cells were greatest at 10, 28, 15, 1, 20 and 4 dpi, although significant differences with control animals were only seen at 10 and 28 dpi. Eosinophils and mast cells showed negative correlation only in animals with second instar larvae (10 and 15 dpi). Comparative analyses were also carried out after considering the skin into four distinct regions. The results suggest that the expression of both cell types, particularly eosinophils, is an important host response to infestation by D. hominis.     

Dermacentor variabilis: acquired resistance to ticks in BALB/c mice

To assess the ability of Dermacentor variabilis larvae to feed on mice during repeated infestations, known numbers of larvae were confined to the skin of BALB/c mice within plastic capsules, and different skin sites were used in four successive infestations. In secondary infestations larval feeding appeared to be enhanced, but in subsequent infestations the mice expressed acquired tick resistance, manifested by reduction in numbers of engorged larvae and in weights of fed larvae. Resistance, once established, was still demonstrable four weeks after the previous infestation. Histological examination of skin biopsies from BALB/c mice undergoing repeated infestations revealed slight reactions to primary infestations and increasingly severe responses in subsequent infestations. The latter reactions included prominent participation of mast cells and eosinophils, many of which were degranulated close to tick bite sites. It is suggested that these cells might play a role in the expression of murine tick resistance.     

Local immune response against larvae of Rhipicephalus (Boophilus) microplus in Bos taurus indicus and Bos taurus taurus cattle

Bos taurus indicus cattle are less susceptible to infestation with Rhipicephalus (Boophilus) microplus than Bos taurus taurus cattle but the immunological basis of this difference is not understood. We compared the dynamics of leukocyte infiltrations (T cell subsets, B cells, major histocompatibility complex (MHC) class II-expressing cells, granulocytes) in the skin near the mouthparts of larvae of R. microplus in B. t. indicus and B. t. taurus cattle. Previously naïve cattle were infested with 50,000 larvae (B. t. indicus) or 10,000 larvae (B. t. taurus) weekly for 6 weeks. One week after the last infestation all of the animals were infested with 20,000 larvae of R. microplus. Skin punch biopsies were taken from all animals on the day before the primary infestation and from sites of larval attachment on the day after the first, second, fourth and final infestations. Infiltrations with CD3⁺, CD4⁺, CD8⁺ and γδ T cells followed the same pattern in both breeds, showing relatively little change during the first four weekly infestations, followed by substantial increases at 7 weeks post-primary infestation. There was a tendency for more of all cell types except granulocytes to be observed in the skin of B. t. indicus cattle but the differences between the two breeds were consistently significant only for γδ T cells. Granulocyte infiltrations increased more rapidly from the day after infestation and were higher in B. t. taurus cattle than in B. t. indicus. Granulocytes and MHC class II-expressing cells infiltrated the areas closest to the mouthparts of larvae. A large volume of granulocyte antigens was seen in the gut of attached, feeding larvae.     

IL-5-dependent conversion of normodense human eosinophils to the hypodense phenotype uses 3T3 fibroblasts for enhanced viability, accelerated hypodensity, and sustained antibody-dependent cytotoxicity

Human peripheral blood-derived eosinophils were assessed for their viability, density, and functional properties after 7 days of culture with purified mouse IL-5 and mouse 3T3 fibroblasts. Whereas none of the eosinophils remained viable after 7 days of culture in the absence of IL-5, 38 +/- 12% and 61 +/- 14% (n = 6, mean +/- SD) of the eosinophils survived in the presence of 1 pM IL-5 alone or 1 pM IL-5 in the presence of 3T3 fibroblasts, respectively (p less than 0.05). Direct contact between the fibroblasts and the eosinophils was not needed for this enhanced IL-5-dependent viability. After 7 days, 66 +/- 7% (n = 6) of the cocultured eosinophils were viable when the two cell types were separated by a 0.4-microns filter. As assessed by density-gradient centrifugation after 7 days of IL-5 exposure, all of the original normodense eosinophils became hypodense. The time course of this conversion was accelerated by the presence of 3T3 fibroblasts. Enhanced helminthic cytotoxicity was maintained by the 7-day cultured eosinophils only if they had been cocultured with fibroblasts. Eosinophils killed 10 +/- 11% (n = 5), 48 +/- 17%, and 31 +/- 15% of the larvae when they were cultured for 7 days in IL-5 alone, in IL-5 in direct contact with 3T3 fibroblasts, or in IL-5 with filter separation of the fibroblasts and the eosinophils, respectively. The ability of IL-5 to induce progenitor cells to differentiate selectively into eosinophils, and of 3T3 fibroblasts to facilitate the IL-5-mediated conversion of normodense eosinophils to hypodense eosinophils with increased viability and antibody-dependent cytotoxicity suggests a role for both hematopoietic and tissue factors in determining the presence and pathobiologic function of activated hypodense eosinophils in patients with hypereosinophilic conditions.     

The changes of histopathology and serum anti-sparganum IgG in experimental sparganosis of mice

The present study is intended to observe the chronologic changes of experimental sparganosis by histopathological observation and detection of circulating anti-sparganum IgG antibody using ELISA. Each of 25 mice was infected with five spargana, and they were examined after 1, 2, 4, 10 weeks or 6 months from infection. The followings are summarized results. 1. The plerocercoids were detected in the subcutaneous tissue of the trunk, neck or axilla, but a few often extended into the skeletal muscle. The recovery rates were 72% at the first week, 80% at the second week, 95% at the fourth week, 92% at the tenth week and 100% at the sixth month. The larvae grew slowly in both length and weight until 6 months. 2. Histopathologically, most of the larvae were observed alive in the soft tissue or skeletal muscle. Numerous eosinophils, neutrophils, lymphocytes and plasma cells were infiltrated focally around the worms by the second week, but they surrounded the worms to form a layer of inflammatory reaction after 4 weeks of infection. Also histiocytes and fibroblasts began to appear around the inflammatory cells at 4 weeks. After 10 weeks, the worms encircled by a thin fibrous layer were found. After 6 months, the worms were surrounded by either fibrous tissue or active inflammatory cells. The inflammation looked more severe in the tracks left by the worms, rather than around the worms. 3. The level of anti-sparganum IgG antibody in the serum showed an increase by the fourth week, and a rapid and continuous increase was observed thereafter by the tenth week after infection.(ABSTRACT TRUNCATED AT 250 WORDS)     

Histopathological appearances in primary and secondary infections with Strongyloides ratti in mice

Dawkins H. J. S., Muir G. M. & Grove D. I. 1981. Histopathological appearances in primary and secondary infections with Strongyloides ratti in mice. International Journal for Parasitology11: 97–103. The histological appearances of the skin, lungs and small intestines of mice with primary and secondary infections with S. ratti are described. When the skins of mice with a primary infection were examined, larvae were seen scattered throughout the dermis. An inflammatory reaction of neutrophils and eosinophils was first noted around larvae 12 h after infection. By 48 h, mononuclear cells were prominent. The intensity of the inflammatory reaction gradually increased to a maximum on the fifth day and the larvae were destroyed. Very few larvae were seen in the lungs; those observed were located in the alveolar spaces and were not surrounded by an inflammatory infiltrate. Worms in the small intestines were found mostly in the crypts of Leiberkuhn, and were probably located within the epithelial layer; there was no significant villous atrophy or cellular infiltration. Marked differences were found in the tissues of mice with secondary infections. In the skin, oedema and neutrophils and eosinophils were seen around worms as early as 2 h after infection. By 24 h after infection, there was a mixed inflammatory infiltrate and worms were undergoing disintegration. Larvae in the lungs were surrounded by polymorphonuclear and mononuclear cells 48 h and 72 h after infection and the engulfed larvae were undergoing lysis. Only a few worms were seen in the intestines of mice with a secondary infection; the histological appearances were similar to that found in animals with primary infections. It is suggested that the rapid development of an oedematous reaction in the skins of immune mice may facilitate the entry of larvae into the bloodstream and that inflammatory cells destroy many larvae in the lungs of immune mice.     

Effects of larval densities and the duration since larval infestation on the host-searching behavior of Diadegma semiclausum, a parasitoid of diamondback moth larvae on plants

The host-searching behavior of Diadegma semiclausum, a parasitoid of diamondback moth (DBM) larvae, was studied in a wind tunnel. Wasps flew preferentially to a cabbage plant, freshly infested by 1 DBM larva, or one freshly infested by 10 DBM larvae, than to an intact plant. There was no significant difference between wasps?? responses to plants infested by different DBM larvae densities. We also found that the duration since the last infestation by 10 DBM larvae (1 or 3?days) negatively affected the attractiveness of infested plants. We also studied the time wasps spent searching for larvae on a cabbage plant (residence time). The wasps spent ca. 400?s on a plant freshly infested by 1 larva. Residence time was significantly longer (ca. 1,200?s) on a plant freshly infested by either 5 or 15 DBM larvae. Residence time of D. semiclausum on a plant freshly infested by 5 DBM larvae was significantly longer than on a previously infested plant (1 or 3?days after the last infestation). These results showed that host densities on a plant and the duration since their last infestation affected the host-searching behavior of D. semiclausum.     

Rabbit antibody responses to experimental infestation with Dermatobia hominis

The three larval stages of Dermatobia hominis (Linnaeus) have been evaluated for their immunogenicity by ELISA and immunodiffusion (ID) using sera from experimentally infested rabbits. During a primary infestation, first instar D. hominis were found to cause most reaction and allowed the earliest diagnosis by ELISA. An inhibition of the antibody response against second and third instars was observed. The inhibition disappeared after departure of the larvae from the host. In experimentally immunized hosts the antibody response, following challenge, was highest against second and third instar antigens. Antibody remained elevated during the infestation but fell immediately after the larvae had left the host.     

Ixodes dammini: Induced skin lesions in guinea pigs and rabbits compared to erythema chronicum migrans in patients with lyme arthritis

Erythematous skin lesions occurred in rabbits 2 days after being fed upon by larvae or nymphs of the tick, Ixodes dammini. Similar lesions occurred in guinea pigs 7 days after a primary infestation with either larvae or nymphs. Host resistance to secondary feeding by larvae was demonstrated in guinea pigs and rabbits. Host resistance to secondary feeding by nymphs was seen in guinea pigs, but not in rabbits. Guinea pigs developed resistance to nymphs after being previously fed upon twice by larvae. All skin lesions in resistant guinea pigs contained large accumulations of basophils (49–76% of cells) with smaller (20–33%), but significant, numbers of eosinophils. These responses were characteristic of strong cutaneous basophil hypersensitivity reactions. Primary and secondary lesions in rabbits fed upon by larvae contained mostly mononuclear cells (46–52%) and moderate numbers (16–30%) of basophils and eosinophils. Primary and secondary lesions in rabbits fed upon by nymphs had few (3–11%) basophils and eosinophils and were dominated by mononuclear cells (73–86%). Thus, acquired resistance in guinea pigs and rabbits was associated with cutaneous basophil and eosinophil responses and the lack of resistance of rabbits to nymphs was associated with erythematous lesions dominated by mononuclear cells. The mononuclear nature of rabbit lesions induced by nymphal feeding was similar to that seen in erythema chronicum migrans in Lyme arthritis patients who are thought to have been fed upon by I. dammini nymphs. This study confirms the cutaneous basophil hypersensitivity characteristics of lesions in guinea pigs resistant to ticks and demonstrates a relationship between the mononuclear cell response of rabbits to nymphal I. dammini and the cellular response seen in patients with erythema chronicum migrans and Lyme arthritis.     

Eosinophil degranulation. An immunologic determinant in the pathogenesis of the Mazzotti reaction in human onchocerciasis

Onchocerciasis patients treated with diethylcarbamazine often undergo a severe inflammatory response, the Mazzotti reaction. To assess the eosinophil's role in the pathogenesis of the Mazzotti reaction, we obtained serial blood, plasma, and skin biopsy specimens from 21 heavily infected patients and 3 endemic controls, both before and during therapy with diethylcarbamazine. Samples were analyzed for blood eosinophils, plasma levels of eosinophil granule major basic protein (MBP) and eosinophil-derived neurotoxin, eosinophil infiltration and eosinophil and mast cell degranulation in the skin. After the first dose of diethylcarbamazine, blood eosinophils fell from a pre-treatment level of 888 +/- 111 to 203 +/- 42 cells/mm3 at 8 h. This decrease was followed by a marked eosinophilia developing over the remaining 7 days of treatment and 14 days of follow-up. Plasma eosinophil-derived neurotoxin levels increased from 56 +/- 4 ng/ml pretreatment to a peak of 82 +/- 9 ng/ml at 8 h and returned to pretreatment levels by 48 h. Beginning at 12 h, plasma MBP levels increased from 730 +/- 74 ng/ml pretreatment to a peak of 1140 +/- 74 ng/ml after 5 days. Pretreatment skin biopsies stained for MBP by immunofluorescence showed a bright fibrillar pattern in the dermis consistent with chronic eosinophil degranulation; the MBP was localized on elastic tissue fibers. After treatment, skin biopsy specimens showed both the pretreatment fibrillar MBP staining pattern as well as focal eosinophil degranulation. Deposition of MBP around microfilariae in the papillary dermis was visible as early as 1.5 h. The lowest blood eosinophil levels and peak plasma eosinophil-derived neurotoxin levels coincided with the infiltration and degranulation of eosinophils in the skin. Mast cell degranulation in the skin was maximal by the first posttreatment biopsy (1.5 h) coincident with the beginning of eosinophil degranulation. Although the pathogenesis of the Mazzotti reaction is clearly complex, our results indicate that eosinophil degranulation is characteristic of the response and that it occurs with a time course suggestive of a role for the eosinophil in determining the clinical and pathologic manifestations of the reaction.     

Histological and immunological reaction of cattle skin to first-instar larvae of Dermatobia hominis

Abstract. Six cattle that had earlier exposure to Dermatobia hominis were infested experimentally with first-instar larvae of the parasite. Skin biopsies taken at intervals were studied in wax and in plastic sections. The avidin-biotin-peroxidase method was used to detect the presence and localization of host immunoglobulins (Igs) G and M and antigens of first and second instar larvae of Dermatobia hominis. The larvae penetrated actively through the skin and migrated towards the subcutaneous tissues. The great numbers of eosinophils suggest that they are the most important cell in mediating damage to D.hominis larvae. The immunoglobulins bound only to dead or moulting larvae in which access to binding sites may have been altered. This could represent a morphological manifestation of a mechanism that protects larvae from the host immune response. Large amounts of soluble antigens detected along the fistulous tract may be important in the maintenance of this tract by disturbing the normal cicatrization process.     

Attractivity of cattle infested by Amblyomma variegatum (Acari: Ixodidae) for conspecific adult ticks from the field in Guadeloupe

Four field experiments were conducted with creole cattle in Guadeloupe to study the attractivity for adult ticks of animals previously infested with males of Amblyomma variegatum producing aggregation attachment pheromones (AAPs). In each experiment, two groups of cattle were used; the first group was infested with adult A. variegatum and the second group was kept free of ticks and pheromones by acaricidal treatment and by washing the hair and skin of previously infested sites. Both groups were then exposed to natural infestation by ticks present in the environment or by ticks bred in the laboratory and released on the pasture. The number of additional ticks infesting animals were compared between the treated and control groups. There were no significant differences between both groups in the numbers of new male ticks infesting the animals during the first days following the beginning of the experiment. Thereafter, comparison of the slopes of infestation indicated that infested cattle were no more attractive for male ticks than uninfested hosts. Uninfested cattle were spontaneously and rapidly infested by male ticks. It is concluded that carbon dioxide or another host component was a major attractant for A. variegatum males. Female ticks attached on predilection sites exclusively in the presence of AAP-producing males, i.e. 5–10 days after the attachment of the first males. Based on these results we postulate that slow-release devices impregnated with pheromones have no additional attractive effect on A. variegatum males under Caribbean conditions. However, they may be useful in inducing the attachment of females, but only in the first days preceding the arrival of pioneer AAP-producing males. © Rapid Science Ltd. 1998     

Vitamin B6-deficient diet plus 4-deoxypyridoxine (4-DPD) reduces the inflammatory response induced by T. spiralis in diaphragm,masseter and heart muscle tissue of mice

Animals fed diets deficient in vitamin B6 develop microcytic anemia, alterations of growth, and other pathologies. 4-deoxypirydoxine is a potent antagonist of vitamin B6 coenzyme which depresses IL-1, TNF and IL-6 and has anti-inflammatory properties. The aim of this study was to show the anti-infl ammatory effects of 4-DPD on chronic inflammation caused by the nematode parasite T. spiralis, specifically on the recruitment and the activation of inflammatory cells. Two groups of mice, 6 weeks of age, were used: one was maintained on a vitamin B6-deficient synthetic pellet diet for 15 days before injection of the nematode, and administered an intraperitoneal injection (i.p.) of 4-DPD (250 g/mouse) for 15 days (the first, 5 days before infection), and the second group was maintained on a normal diet for the total duration of the experiment. These two groups were then injected with 150 larvae (L1-T. spiralis) per os.Chronic inflammation was caused by infection of treated or untreated mice with T. spiralis parasite. After 14 days post-infection all mice developed a chronic inflammatory response. Mice fed with a B6-deficient diet showed a significant decrease in the number of cysts found in the diaphragm when compared to mice treated with normal diet. In addition, in all mice treated with vitamin B6-deficient diet plus 4-DPD the average body weight was significantly lower, compared to the mice on normal diet in all weeks examined. Moreover, in sections of the diaphragm, masseter and miocardium muscles, the infiltration of inflammatory cells, such as macrophages, lymphocytes, and eosinophils were more intense in untreated mice compared to those fed a vitamin B6-deficient diet.These results show that BALB/c mice infected with T. spiralis and fed a vitamin B6-deficient diet plus the vitamin B6 antagonist, 4-DPD, prolong the time of invasion of the larvae in the muscle cells, influence the recruitment of inflammatory cells and the intensity of the inflammatory reaction compared to infected untreated mice (control)     

Experimental Haemonchus contortus infections in guinea pigs

Approximately 40% of exsheathed Haemonchus contortus larvae administered to guinea pigs established in the stomach and developed into fourth stage larvae. Most worms were then lost between 5 and 7 days after infection and the guinea pigs were resistant to a second infection. Haemorrhage, oedema and infiltration with inflammatory cells, especially eosinophils, developed in the stomach wall of infected guinea pigs and reactive hyperplastic changes occurred in the gastric lymph node. H. contortus infection of guinea pigs has some potential as a model for study of the pathology, immunology and chemotherapy of gastric nematodiasis.     

The relationship between infiltrating CD4+ lymphocytes, activated eosinophils, and the magnitude of the allergen-induced late phase cutaneous reaction in man

The phenotype and activation status of leukocytes infiltrating human late phase allergic skin reactions were investigated by immunocytochemistry using a panel of mAb. Late phase skin reactions were induced in atopic individuals by intradermal challenge with allergen extract (grass pollen or house dust mite) and skin biopsies were obtained 6, 24, or 48 h after challenge. Cryostat sections were examined for evidence of infiltration and activation of T cells and eosinophils. Biopsies from saline-challenged control sites were used for comparison. A substantial number of CD3+ cells were observed close to the dermal capillaries. The number of CD4+ cells showed a similar pattern but few CD8+ cells were seen. The ratio of CD4 and CD8 subsets in tissue did not relate to the CD4/CD8 ratio in the peripheral blood. Two observations suggested that T cells had become activated: first, a small number of infiltrating cells bore receptors for IL-2, and second, there was indirect evidence of IFN-gamma secretion, demonstrated by increased expression of HLA-DR on endothelial cells and de novo expression of CD4 Ag on epidermal Langerhans cells. Activated eosinophils were detected in most of the allergen-challenged biopsies. The late phase reaction diameter at 6 h correlated with the number of activated eosinophils at 48 h (r = 0.61, p = 0.05), but not with infiltration by T cells. There was a strong correlation between the numbers of CD4+ cells and activated eosinophils at 24 h (r = 0.94, p less than 0.001). These findings suggest that interactions between T lymphocytes and eosinophils in reactions to airborne allergens may be more important than has previously been recognized.     

Effects produced by the feeding of larvae of <Emphasis Type="Italic">Ornithodoros</Emphasis> aff. <Emphasis Type="Italic">puertoricensis</Emphasis> (Acari: Argasidae) on laboratory mice

The clinical picture produced by the feeding of larvae of Ornithodoros aff. puertoricensis on laboratory mice, was studied using different larval infestation protocols that included 30, 40 or 50 larvae per mouse and control uninfested groups. Clinical effects appeared around 72 h of larval feeding, having a first stage characterized by hyperaemia in both nasal and ocular mucosa, followed by respiratory symptoms (96–120 h) and nervous incoordination (120–144 h). No one mouse evidenced paralysis, and nervous symptoms were never observed in animals infested with only 30 larvae. High mortality (commonly up to 70%) was observed in mice with respiratory symptoms, while 100% of animals in the nervous phase died between 168 and 192 h after the beginning of larval feeding. When some infested mice were treated with a solution of Amitraz the larvae were killed and reversion of symptoms was observed. These effects are ascribed to the presence of a toxin in the saliva of the feeding larvae.     

The nutritive value of dying maize and Setaria faberi roots for western corn rootworm (Coleoptera: Chrysomelidae) development

The timing that dying root tissues of Setaria faberi R.A.W. Herrm. and maize, Zea mays L., no longer support growth and development of neonate and second-instar western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), larvae was evaluated to enhance our understanding of the basic ecology of this pest. Three separate greenhouse experiments were conducted. In the first experiment, glyphosate was used to kill S. faberi. In the second experiment, glyphosate was used to kill maize, and in the final experiment, maize was killed by severing it below the growing point. These experiments evaluated western corn rootworm larvae for survival and growth parameters among living control plants, plants severed or sprayed on the day they were infested, plants severed or sprayed 5 and 10 d before they were infested, and plants planted 5 and 10 d early and severed or sprayed 5 and 10 d before they were infested (the last two treatments were controls for root size). Larvae were sampled from each of these treatments 5, 10, and 15 d after infestation, and beetle emergence was recorded from the remaining pots. When infested on the day of glyphosate spray, significantly fewer larvae were recovered from S. faberi than from living S. faberi. Overall, when infested 5 or 10 d after being sprayed with glyphosate or being severed below the growing point, no significant larval weight gain was recorded from any treatment. Host plant tissue apparently becomes unsuitable for larval growth within the first 5 d after glyphosate spray and severing below the growing point. The implications of these data toward current work involving alternate grassy hosts sprayed with herbicide, the increasing occurrence of volunteer corn, related studies on rootworm-host interactions, and certain adult emergence techniques are discussed along with possible mechanisms as to why the tissue becomes unsuitable so quickly.     

Growth and development of winter tick, Dermacentor albipictus, on moose, Alces alces

Moose, Alces alces, were infested with 21,000 or 42,000 larval Dermacentor albipictus at the end of September. Larvae grew rapidly and molted to the nymphal stage 10-22 days after infestation. The nymphal stage lasted approximately 3 mo until mid-January and was characterized by a diapause. The diapause is likely an adaptation to survival in cold climates. Nymphs started engorging in January and adults were seen with increasing abundance from mid-January to March and April. The minimum parasitic period was 175 days. Growth of larvae and nymphs was similar on moose given different numbers of larvae and was generally similar between a moose infested in November and moose infested earlier. Dimensions and stages of development throughout the parasitic phase are given. Game enforcement officers are encouraged to use these data for determination of season of death of moose.     

Parasitism by the mite Trombidium breei on four U.K. butterfly species

Abstract 1.  The incidence of parasitism by larvae of the mite species Trombidium breei was reported in one population of the lycaenid butterfly Polyommatus icarus , four populations of the satyrine butterfly Maniola jurtina , one population of the satyrine butterfly Aphantopus hyperanthus , and two populations of the satyrine butterfly Pyronia tithonus , as well as on one specimen of the dipteran Alophorus hemiptera . A considerable proportion of butterflies (11-50%) was infested in all study populations.
2. The pattern of infestation was examined in detail in M. jurtina . Males had a significantly higher incidence of infestation than females, and middle-aged butterflies had a higher incidence of infestation than old or young butterflies. The incidence of infestation peaked in the middle of the flight season, and this seasonal effect was independent of the effect of butterfly age.
3. Using a model based on capture-recapture data, it was estimated that a hypothetical ideal male M. jurtina that lives exactly the mean expected lifespan of 9-10 days has an approximately 75% chance of becoming infested with mites at least once during its lifetime, a mean time to first infestation of 3-4 days, and an average infestation persistence time of 2-3 days.
4. Capture-recapture data failed to show any effect of mite infestation on the lifespan or within-habitat movement rate of M. jurtina .
5. In experiments in which individual butterflies were taken out of their normal habitat and released, M. jurtina and P. tithonus that were infested with mite larvae did not differ from uninfested individuals in the efficiency with which they returned to suitable habitat. Thus, parasitism by T. breei larvae had no detectable effects on flight performance or orientation ability.
6. The results suggest that trombidiid mite larvae have limited potential in the biological control of insect pests.