Base-line susceptibility of Phlebotomus papatasi to insecticides

Susceptibility of the leishmaniasis vector sandfly Phlebotomus papatasi (Scopoli) to three insecticides was assessed on a colony originating in the Jordan Valley, Israel. Results are considered to show susceptibility to DDT and permethrin. The results for methoxychlor indicated the possibility of heterogeneity in the population and tolerance towards this compound.     

Sandfly midgut lectin: effect of galactosamine on Leishmania major infections

Galactosamine, which has been shown in vitro to specifically inhibit sandfly midgut lectin activity, was fed to Phlebotomus duboscqi females with blood containing promastigotes of Leishmania major . Non-inhibitory sugar, galactose, was added in controls. For two strains of L. major (LV 561 and Neal-P), galactosamine substantially enhanced the establishment of infection in the sandfly posterior midgut and significantly increased parasite loads after defaecation, but did not affect anterior migration of Leishmania . On day 3 post-infection, most infections in galactosamine-fed sandfly groups (92% of LV 561 and 100% of Neal-P) were found in the ectoperitrophic space of the posterior midgut, whereas most infections in the galactose-fed groups of sandflies (85% in LV 561 and 96% in Neal-P) were restricted to the peritrophic sac. On day 9, however, the proportion of infections colonizing the stomodeal valve was similar in both dietary groups of sandflies for both strains of L. major . The addition of galactosamine prevented the decrease of parasite loads which occurred in controls between days 3 and 6 post-infection. On days 6 and 9, heavy infections were observed almost exclusively in galactosamine-fed females. Differences between groups were more pronounced for the Neal-P strain, which normally developed poorly in sandflies. Morphology of L. major LV 561 was not affected by galactosamine supplement: the lengths of parasite body and flagellum were similar in both sandfly groups. Two hypotheses are considered for the role of sandfly midgut lectin in Leishmania development in the vector midgut. One proposes that sandfly lectin kills Leishmania promastigotes, the other assumes that lectin blocks LPG-mediated binding of promastigotes to sandfly midgut microvilli.     

Sandfly pheromones. Their biology and potential for use in control programs

Lutzomyia longipalpis (Diptera: Psychodidae) is the vector of Leishmania chagasi the causative agent of visceral leishmaniasis (VL) in South and Central America, particularly Brazil, where the greatest incidence occurs. The disease is fatal if untreated. Although huge efforts have been made to control VL the incidence is increasing. Vector control remains an important element of disease control but residual spraying and other strategies have failed to make any lasting impact. Manipulation of sandfly chemical communication offers the opportunity to add new techniques and tools to reduce sandfly populations and thereby reduce Leishmania transmission. This paper reports the current understanding of several areas of sandfly chemical ecology and their prospects for application.     

Establishment of a colony, in laboratory, of Lutzomyia intermedia Lutz & Neiva, 1912 (Diptera, Psychodidae, Phlebotominae)

A laboratory colony of the sandfly Lutzomyia intermedia was established (at present in its seventh generation) in order to provide specimens for experimental infection and for experimental xenodiagnosis of natural infections due to cutaneous leishmanias in Rio de Janeiro. Date are presented on the methodology and on the yield and duration of each stage of development, during the first four generations.     

Distribution of sandflies (Diptera:Psychodidae) on tree-trunks in a non-flooded area of the Ducke Forest Reserve, Manaus, AM, Brazil.

Sandflies were collected in the base of tree-trunks in the seasons of high and least rainfall in the Ducke Forest Reserve, near Manaus in the State of Amazonas. Lutzomyia umbratilis was the most abundant sandfly species. Caryocar villosum, Chrysophyllum amazonicum, Dinizia excelsa, Eschweilera atropetiolata and Parkia multijuga were the tree species on which most sandflies were collected and relative abundance were related to trunk characteristics. Seasonal patterns of sandfly distribution in the forest were observed.     

Oviposition behaviour of Phlebotomus argentipes - A laboratory-based study

The breeding habitat of sandflies is a little studied and poorly understood phenomenon. More importantly, oviposition behaviour is a largely neglected aspect of sandfly biology and this knowledge gap further undermines our understanding of the biology of sandflies. Pheromones released by the eggs play an important role in identifying good sites for oviposition by female insects. Several recent studies have examined the oviposition pheromone. The present study provides a preliminary report on the oviposition behaviour of Phlebotomus argentipes, the only vector of kala-azar (or visceral leishmaniasis) on the Indian sub-continent. Sandflies prefer to oviposit their eggs on surfaces that contain organic substances, especially substances with an odour of decaying animal products and the remains of conspecific eggs. The results presented here suggest that the odour released by the organic substances of old sandfly colony remains that contain dead flies, old unhatched eggs, larval food containing vertebrate faeces, frass and other organic matter serves as an attractant for the ovipositing females of P. argentipes and hence greatly increases the number of oviposited eggs compared to eggs deposited in controlled oviposition pots. This result will be helpful in maintaining an efficient colony of P. argentipes and may be a promising tool for monitoring and controlling the target insect as part of a synergistic approach.     

Leishmania-sandfly interactions: an empirical field study

Phlebotomus papatasi is the sandfly vector of Leishmania major in the Jordan Valley. The objective of this study was to characterize vector-parasite relations in an active zoonotic focus. Seasonality and intensity of promastigote infection rates in female sandflies and the developmental stage of these hosts were established. On 153 trap-nights, 641 female P. papatasi were caught and examined. Of these, 48 (7.4%, range 12.9-4.8%) were infected with L. major promastigotes. Correlating the number of parasites with the gonotrophic age of the vector revealed that most infections initially are light ones, and those that survive in the vector generally prosper and proliferate. Comparing infection rates in parous and gravid flies revealed that similar proportions of gravid and parous flies are found infected. Thus, Leishmania infections do not appear to affect sandfly survival.     

Unicoloniality in Reticulitermes urbis: a novel feature in a potentially invasive termite species

Social insects are among the world's most successful species at invading of new habitats. A good example of this invasive ability is Reticulitermes (Rhinotermitidae), a prominent group of subterranean termites. As a result of human intervention, i.e. transportation and creation of urban heat islands, Reticulitermes have been able to invade and thrive in cities located in areas where the natural habitat is normally too cold for colonization. They commonly infest man-made structures where they can cause extensive damage.This study was designed to evaluate the invasiveness of Reticulitermes urbis that was probably introduced in France from the Balkans. Invasive potential was assessed on the basis of features typical to invasive social insects, i.e. unicoloniality, low intraspecific aggression, high level of polygyny and colony reproduction by budding. The opportunity to study establishment and spreading processes arose after extensive sampling of an imported Reticulitermes urbis population was performed over the entire city of Domène, France (Rh?ne-Alpes region).For the first time, genetic analysis showed that the termites belonged to a single 'genetic entity' forming a vast colony covering about seven hectares. The colony was structured as an extended family with separate reproductive centres. We speculate that termites were introduced in a single location from which they gradually budded throughout the old town. Based on the absence of aggression among different nests within the colony, we defined this 'genetic entity' as a supercolony.     

Phlebotomine sandfly ecology on the Indian subcontinent: does village vegetation play a role in sandfly distribution in Bihar,India?

Visceral leishmaniasis (VL) is a disease that results in approximately 50 000 human deaths annually. It is transmitted through the bites of phlebotomine sandflies and around two‐thirds of cases occur on the Indian subcontinent. Indoor residual spraying (IRS), the efficacy of which depends upon sandfly adults resting indoors, is the only sandfly control method used in India. Recently, in Bihar, India, considerable sandfly numbers have been recorded outdoors in village vegetation, which suggests that IRS may control only a portion of the population. The purpose of this study was to revisit previously published results that suggested some sandflies to be arboreal and to rest on outlying plants by using Centers for Disease Control light traps to capture sandflies in vegetation, including banana plants and palmyra palm trees, in two previously sampled VL‐endemic Bihari villages. Over 3500 sandflies were trapped in vegetation over 12 weeks. The results showed the mean number of sandflies collected per trap night were significantly higher in banana trees than in other vegetation (P = 0.0141) and in female rather than male palmyra palm trees (P = 0.0002). The results raise questions regarding sandfly dispersal, oviposition and feeding behaviours, and suggest a need to refine current control practices in India and to take into account an evolving understanding of sandfly ecology.     

Sandfly maxadilan exacerbates infection with Leishmania major and vaccinating against it protects against L. major infection.

Bloodfeeding arthropods transmit many of the world's most serious infectious diseases. Leishmania are transmitted to their mammalian hosts when an infected sandfly probes in the skin for a bloodmeal and injects the parasite mixed with its saliva. Arthropod saliva contains molecules that affect blood flow and modulate the immune response of the host. Indeed, sandfly saliva markedly enhances the infectivity of L. major for its host. If the salivary molecule(s) responsible for this phenomenon was identified, it might be possible to vaccinate the host against this molecule and thereby protect the host against infection with Leishmania. Such an approach represents a novel means of controlling arthropod-borne disease transmission. Here, we report that a single molecule, maxadilan, in sandfly saliva can exacerbate infection with L. major to the same degree as whole saliva, and that vaccinating against maxadilan protects mice against infection with L. major.     

Why join a neighbour: fitness consequences of colony fusions in termites

The evolution of life is characterized by major evolutionary transitions during which independent units cooperated and formed a new level of selection. Relatedness is a common mechanism that reduces conflict in such cooperative associations. One of the latest transitions is the evolution of social insect colonies. As expected, they are composed of kin and mechanisms have evolved that prevent the intrusion of nonrelatives. Yet, there are exceptions an extreme case is the fusion of unrelated colonies. What are the advantages of fusions that have colonies with a high potential for conflict as a consequence? Here, we investigated fitness costs and benefits of colony fusions in a lower termite species, Cryptotermes secundus, in which more than 25% of all colonies in the field are fused. We found two benefits of colony fusion depending on colony size: very small colonies had an increased probability of survival when they fused, yet for most colony sizes mainly a few workers profit from colony fusions as their chance to become reproductives increased. This individual benefit was often costly for other colony members: colony growth was reduced and the current reproductives had an increased chance of dying when fusions were aggressive. Our study suggests that fusion of colonies often is the result of ‘selfish’ worker interests to become reproductives, and this might have been important for the termites' social evolution. Our results uniquely shows that selfish interests among related colony members can lead to the formation of groups with increased potential for conflict among less related members.     

Theories of cell ageing: a case of mistaken identity

In social insects which reproduce by colony fission there is often only one queen in each swarm (e.g. honeybees, army ants) and the number of males greatly exceeds the number of new queens produced at swarming time. This seems to contradict Fisher's principle that there should be equal investment in male and female reproductives. Hamilton 1975 has suggested that the principle can be saved by counting the investment in the swarm as part of the investment in female reproductives. Craig 1980, on the other hand, argues that few queens are produced because any further investment in queens would be wasted since a queen without a swarm is valueless; on this view the sex ratio is male-biased because of local competition between queens for swarms. The present paper investigates from first principles how many males should be produced by a species which reproduces by colony fission and how the workers should divide themselves between the new colonies. The results of the analysis do not support Hamilton's conjecture but show that a number of factors are involved in the evolution of male production, including kin selection and the relationship between the “fitness” of a colony and the number of workers in it.     

Relationship between digestive enzymes and food habit of Lutzomyia longipalpis (Diptera: Psychodidae) larvae: Characterization of carbohydrases and digestion of microorganisms

The sandfly Lutzomyia longipalpis (Lutz and Neiva, 1912) is the main vector of American Visceral Leishmaniasis. In spite of its medical importance and several studies concerning adult digestive physiology, biochemistry and molecular biology, very few studies have been carried out to elucidate the digestion in sandfly larvae. Even the breeding sites and food sources of these animals in the field are largely uncharacterized. In this paper, we describe and characterize several carbohydrases from the gut of L. longipalpis larvae, and show that they are probably not acquired from food. The enzyme profile of this insect is consistent with the digestion of fungal and bacterial cells, which were proved to be ingested by larvae under laboratory conditions. In this respect, sandfly larvae might have a detritivore habit in nature, being able to exploit microorganisms usually encountered in the detritus as a food source.     

Non-destructive genotyping and genetic variation of fanning in a honey bee colony

The relationship between workers from different patrilines in a naturally mated queen honey bee colony is very complex due to queen polyandry, and still poorly characterized. Here, we report a means of determining the genotype of living workers in a natural honey bee colony by a new non-destructive method, which makes it possible to observe the relationship between behaviours and genotypes. DNA was extracted from the exuvia, found at the bottom of each brood cell, and confirmed to be identical to the DNA extracted from the thorax muscle of the bee emerging from that particular cell. The genotypes were thus determined using DNA from the exuviae without having to hurt or kill the organisms. The emerging workers were marked with coloured, numbered tags to enable behavioural observations over their entire life. Using this new method, we determined 20 patrilines in a naturally mated queen colony, and discovered that the patriline composition of bees exhibiting fanning behaviour was significantly different from the patriline composition of the whole colony. Our results confirm that the genetic structure of a natural insect society plays a fundamental role in the division of labour. The new non-destructive method reveals a novel avenue for the determination of relationships between the behaviours and genes of social insects.     

Lutzomyia longipalpis and the eco-epidemiology of American visceral leishmaniasis, with particular reference to Brazil: a review

An historical review is given of American visceral leishmaniasis (AVL), with particular reference to the eco-epidemiology of the disease in Brazil. Following the first records of AVL in this country, in 1934, the sandfly Lutzomyia longipalpis (Lutz and Neiva, 1912) was incriminated as the principal vector. It is now generally accepted, however, that there exist a number of cryptic species under the name of Lu. longipalpis s.l. and that variations in the quantity of the vasodilatory peptide maxadilan in the saliva of flies from different populations of Lu. longipalpis s.l., may account for the variable clinical manifestations of AVL seen in different geographic regions. Distribution of AVL has been shown to extend throughout most of South and Central America, with the domestic dog serving as the principal reservoir of infection for man. However, while one hypothesis suggests that the causative parasite is Leishmania infantum, imported from Europe with the Portuguese and Spanish colonists, the demonstration of a high rate of benign, inapparent infection in foxes in Amazonian Brazil raised an opposing suggestion that the parasite is indigenous to the Americas. Recent reports of similar infections in native marsupials, and possibly rodents, tend to support this view, particularly as Lu. longipalpis is primordially a silvatic sandfly. Although effective control measures in foci of the disease will diminish the number of canine and human infections, the presence of such an enzootic in a variety of native animals will render the total eradication of AVL unlikely.     

Assessing the importance of four sandfly species (Diptera: Psychodidae) as vectors of Leishmania mexicana in Campeche,Mexico

Localized cutaneous leishmaniasis represents a public health problem in many areas of Mexico, especially in the Yucatan Peninsula. An understanding of vector ecology and bionomics is of great importance in evaluations of the transmission dynamics of Leishmania parasites. A field study was conducted in the county of Calakmul, state of Campeche, during the period from November 2006 to March 2007. Phlebotomine sandfly vectors were sampled using Centers for Disease Control light traps, baited Disney traps and Shannon traps. A total of 3374 specimens were captured in the two villages of Once de Mayo (93.8%) and Arroyo Negro (6.1%). In Once de Mayo, the most abundant species were Psathyromyia shannoni, Lutzomyia cruciata, Bichromomyia olmeca olmeca and Psychodopygus panamensis (all: Diptera: Psychodidae). The Shannon trap was by far the most efficient method of collection. The infection rate, as determined by Leishmania mexicana‐specific polymerase chain reaction, was 0.3% in Once de Mayo and infected sandflies included Psy. panamensis, B. o. olmeca and Psa. shannoni. There were significant differences in human biting rates across sandfly species and month of sampling. Ecological niche modelling analyses showed an overall overlap of 39.1% for the four species in the whole state of Campeche. In addition, the finding of nine vector–reservoir pairs indicates a potential interaction. The roles of the various sandfly vectors in Calakmul are discussed.     

Development of a Flow-Trough Microarray based Reverse Transcriptase Multiplex Ligation-Dependent Probe Amplification Assay for the Detection of European Bunyaviruses

It is suspected that apart from tick-borne encephalitis virus several additional European Arboviruses such as the sandfly borne Toscana virus, sandfly fever Sicilian virus and sandfly fever Naples virus, mosquito-borne Tahyna virus, Inkoo virus, Batai virus and tick-borne Uukuniemi virus cause aseptic meningo-encephalitis or febrile disease in Europe. Currently, the microarray technology is developing rapidly and there are many efforts to apply it to infectious diseases diagnostics. In order to arrive at an assay system useful for high throughput analysis of samples from aseptic meningo-encephalitis cases the authors developed a combined multiplex ligation-dependent probe amplification and flow-through microarray assay for the detection of European Bunyaviruses. These results show that this combined assay indeed is highly sensitive, and specific for the accurate detection of multiple viruses.     

Responses to damage in an arborescent bryozoan: Effects of injury location

A common consequence of the predation or physical disturbance of sessile modular animals is the removal of part of the colony. This damage is often sub-lethal, and leaves the remainder of the colony to repair and regenerate lost tissue. Damage may, however, have lasting effects on the life history characteristics of a colony. We examined the effects of damage on growth and reproduction in the arborescent bryozoan Bugula neritina (Linnaeus), with a particular focus on the effects of the location of that damage. We predicted that a damaged colony would initially allocate more energy to damage repair and subsequent growth, increasing in size to decrease the risk of mortality, at the expense of its short-term reproductive potential. A short-term experiment assessed the immediate regenerative capacities of colonies, while a longer-term experiment measured overall colony responses to damage at different colony locations. In this experiment, zooids were removed in three colony regions; all on one colony branch, spread evenly across all growing tips, and a third, intermediate pattern. A third experiment tested the effects of predator-induced damage versus damage alone, by measuring the recovery of colonies subjected to either a predation event by the nudibranch Polycera hedgpethi, or to an imitation predation event, where an equivalent section of the colony was removed manually. Regeneration was rapid, with budding resuming a few days after damage occurred. Removing around 20% of the colony did not consistently alter colony growth rates in any experiment, but the onset of reproduction was delayed by 7 to 20 days, and subsequent colony fecundity reduced by as much as 70% in one damage treatment. The removal of the same amount of tissue by nudibranch predators, or manually removed in a treatment that mimicked this predation, had no detrimental effect on the onset of reproduction or the eventual reproductive output. Nudibranchs removed tissue by consuming whole colony branches, and the experimental treatment that removed one branch also had the least effect of three damage treatments. These results suggest the severity of long-term effects depends on the location of the injury, and that B. neritina does not modify its growth or reproductive patterns to minimise these effects.