Seasonal Changes of sandflies: A study of the Endemic Outbreak of Leishmania Major in Zagora, Southeast Morocco

Leishmaniasis is endemic in the province of Zagora and presents a real danger to the health situation. It is manifested by endemic morbidity. The objective of this study is to assist in vector control measures by providing information on the richness, abundance, seasonal trend, presence and sex ratio of sand fly species in this active epidemic. The study was conducted in Bleida locality in the province of Zagora, during an outbreak of L. major. The results of this study, undertaken in 2019, showed the predominance of Ph. papatasi (44.8%), followed by Ph. longicuspis (26.3%) and S.schwetzi(8.2%).The analysis supports the involvement of P. papatasi as a vector of L. major in Bleida locality. which indicates the increase of cutaneous leishmania in the province of Zagora.

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Risk Assessment of the Role of the Ecotones in the Transmission of Zoonotic Cutaneous Leishmaniasis in Central Tunisia

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph18179274 ◽

2021 ◽

Vol 18 (17) ◽

pp. 9274

Author(s):

Walid Barhoumi ◽

Ifhem Chelbi ◽

Wasfi Fares ◽

Sami Zhioua ◽

Mohamed Abbas ◽

...

Keyword(s):

Cutaneous Leishmaniasis ◽

Leishmania Major ◽

Etiologic Agent ◽

Control Measures ◽

Sand Fly ◽

Main Peak ◽

Sand Flies ◽

Central Tunisia ◽

Zoonotic Cutaneous Leishmaniasis ◽

Significant Difference

Zoonotic cutaneous leishmaniasis (ZCL), endemic in Central and Southern Tunisia, is caused by Leishmania major (Kinetoplastida: Trypanosomatidae), which is transmitted by the sand fly Phlebotomus papatasi. In Tunisia, the fat sand rat Psammomys obesus and the desert jird Meriones shawi are the principal reservoir hosts of L. major. The presence of the P. papatasi vector of the L. major etiologic agent of ZCL was assessed in the vicinity of villages in endemic areas of Central Tunisia. The study was performed from September through October 2019, a period corresponding to the main peak of activity of P. papatasi. Sand flies were collected from rodent burrows located at the ecotone level, which is the transition zone between the natural environment and human settlement. Sand flies were identified to species level and tested for the presence of L. major by PCR. Our entomological survey showed that P. papatasi is the most abundant sand fly species associated with rodent burrows, and this abundance is even higher in ecotones primarily occupied by P. obesus in comparison to ecotones occupied by M. shawi. Infections with Leishmania major were detected only in P. papatasi, with an overall minimum infection rate (MIR) of 2.64%. No significant difference was observed between the MIRs in ecotones of P. obesus and of M. shawi. Incidence of ZCL in the studied areas ranged from 200 to 700 cases per 100,000 inhabitants, with a mean incidence of 385.41 per 100,000. Higher ZCL incidence was identified in ecotones of M. shawi compared to ecotones of P. obesus. ZCL cases are positively correlated with the MIRs. Considering the short flight range of P. papatasi, increases in its densities associated with burrows of P. obesus or M. shawi at the ecotone level expand the overlap of infected vectors with communities and subsequently increase ZCL incidence. Therefore, control measures should target P. papatasi populations at the ecotones.

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Towards a Sustainable Vector-Control Strategy in the Post Kala-Azar Elimination Era

Frontiers in Cellular and Infection Microbiology ◽

10.3389/fcimb.2021.641632 ◽

2021 ◽

Vol 11 ◽

Author(s):

Rajesh Garlapati ◽

Eva Iniguez ◽

Tiago D. Serafim ◽

Prabhas K. Mishra ◽

Basab Rooj ◽

...

Keyword(s):

Vector Control ◽

Control Strategy ◽

Indoor Residual Spraying ◽

Public Health Problem ◽

Control Measures ◽

World Health ◽

Sand Fly ◽

Current Vector ◽

Kala Azar ◽

Vector Control Strategy

Visceral leishmaniasis (VL) is a potentially deadly parasitic disease. In the Indian sub-continent, VL is caused by Leishmania donovani and transmitted via the bite of an infected Phlebotomus argentipes female sand fly, the only competent vector species in the region. The highest disease burden is in the northern part of the Indian sub-continent, especially in the state of Bihar. India, Bangladesh, and Nepal embarked on an initiative, coordinated by World Health Organization, to eliminate VL as a public health problem by the year 2020. The main goal is to reduce VL incidence below one case per 10,000 people through early case-detection, prompt diagnosis and treatment, and reduction of transmission using vector control measures. Indoor residual spraying, a major pillar of the elimination program, is the only vector control strategy used by the government of India. Though India is close to its VL elimination target, important aspects of vector bionomics and sand fly transmission dynamics are yet to be determined. To achieve sustained elimination and to prevent a resurgence of VL, knowledge gaps in vector biology and behavior, and the constraints they may pose to current vector control methods, need to be addressed. Herein, we discuss the successes and failures of previous and current vector-control strategies implemented to combat kala-azar in Bihar, India, and identify gaps in our understanding of vector transmission towards development of innovative tools to ensure sustained vector control in the post-elimination period.

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High insecticide resistance mediated by different mechanisms in Culex quinquefasciatus populations from the city of Yaoundé, Cameroon

Scientific Reports ◽

10.1038/s41598-021-86850-7 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Abdou Talipouo ◽

Konstantinos Mavridis ◽

Elysée Nchoutpouen ◽

Borel Djiappi-Tchamen ◽

Emmanouil Alexandros Fotakis ◽

...

Keyword(s):

Insecticide Resistance ◽

Vector Control ◽

High Resistance ◽

Culex Quinquefasciatus ◽

Control Strategies ◽

Cuticular Hydrocarbon ◽

Control Measures ◽

High Frequencies ◽

The City ◽

Integrated Vector Control

AbstractCulex mosquitoes particularly Culex quinquefasciatus are important arboviral and filariasis vectors, however despite this important epidemiological role, there is still a paucity of data on their bionomics. The present study was undertaken to assess the insecticide resistance status of Cx. quinquefasciatus populations from four districts of Yaoundé (Cameroon). All Culex quinquefasciatus populations except one displayed high resistance to bendiocarb and malathion with mortalities ranging from 0 to 89% while high resistance intensity against both permethrin and deltamethrin was recorded. Molecular analyses revealed high frequencies of the ACE-1 G119S mutation (ranging from 0 to 33%) and kdr L1014F allele (ranging from 55 to 74%) in all Cx. quinquefasciatus populations. Significant overexpression was detected for cytochrome P450s genes CYP6AA7 and CYP6Z10, as well as for Esterase A and Esterase B genes. The total cuticular hydrocarbon content, a proxy of cuticular resistance, was significantly increased (compared to the S-lab strain) in one population. The study confirms strong insecticide resistance mediated by different mechanisms in Cx. quinquefasciatus populations from the city of Yaoundé. The expansion of insecticide resistance in Culex populations could affect the effectiveness of current vector control measures and stress the need for the implementation of integrated vector control strategies in urban settings.

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A novel role for the peritrophic matrix in protecting Leishmania from the hydrolytic activities of the sand fly midgut

Parasitology ◽

10.1017/s0031182097001510 ◽

1997 ◽

Vol 115 (4) ◽

pp. 359-369 ◽

Cited By ~ 99

Author(s):

P. F. P. PIMENTA ◽

G. B. MODI ◽

S. T. PEREIRA ◽

M. SHAHABUDDIN ◽

D. L. SACKS

Keyword(s):

Digestive Enzymes ◽

Leishmania Major ◽

Specific Inhibitor ◽

Sand Fly ◽

Peritrophic Matrix ◽

Phlebotomus Papatasi ◽

Hydrolytic Activities ◽

Natural Vector ◽

Parasite Survival

The role of the peritrophic matrix (PM) in the development of Leishmania major infections in a natural vector, Phlebotomus papatasi, was investigated by addition of exogenous chitinase to the bloodmeal, which completely blocked PM formation. Surprisingly, the absence of the PM was associated with the loss of midgut infections. The chitinase was not directly toxic to the parasite, nor were midgut infections lost due to premature expulsion of the bloodmeal. Most parasites were killed in chitinase-treated flies within the first 4 h after feeding. Substantial early killing was also observed in control flies, suggesting that the lack of PM exacerbates lethal conditions which normally exist in the blood-fed midgut. Early parasite mortality was reversed by soybean trypsin inhibitor. Allosamadin, a specific inhibitor of chitinase, led to a thickening of the PM, and also prevented the early parasite mortality seen in infected flies. Susceptibility to gut proteases was extremely high in transitional-stage parasites, while amastigotes and fully transformed promastigotes were relatively resistant. A novel role for the PM in promoting parasite survival is suggested, in which the PM creates a barrier to the rapid diffusion of digestive enzymes, and limits the exposure of parasites to these enzymes during the time when they are especially vulnerable to proteolytic damage.

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Phlebotomus papatasi Antimicrobial Peptides in Larvae and Females and a Gut-Specific Defensin Upregulated by Leishmania major Infection

Microorganisms ◽

10.3390/microorganisms9112307 ◽

2021 ◽

Vol 9 (11) ◽

pp. 2307

Author(s):

Barbora Kykalová ◽

Lucie Tichá ◽

Petr Volf ◽

Erich Loza Telleria

Keyword(s):

Gene Expression ◽

Antimicrobial Peptides ◽

Leishmania Major ◽

Larval Instar ◽

Gut Bacteria ◽

Sand Fly ◽

Control Group ◽

Phlebotomus Papatasi ◽

Major Infection ◽

Defensin Gene

Phlebotomus papatasi is the vector of Leishmania major, causing cutaneous leishmaniasis in the Old World. We investigated whether P. papatasi immunity genes were expressed toward L. major, commensal gut microbes, or a combination of both. We focused on sand fly transcription factors dorsal and relish and antimicrobial peptides (AMPs) attacin and defensin and assessed their relative gene expression by qPCR. Sand fly larvae were fed food with different bacterial loads. Relish and AMPs gene expressions were higher in L3 and early L4 larval instars, while bacteria 16S rRNA increased in late L4 larval instar, all fed rich-microbe food compared to the control group fed autoclaved food. Sand fly females were treated with an antibiotic cocktail to deplete gut bacteria and were experimentally infected by Leishmania. Compared to non-infected females, dorsal and defensin were upregulated at early and late infection stages, respectively. An earlier increase of defensin was observed in infected females when bacteria recolonized the gut after the removal of antibiotics. Interestingly, this defensin gene expression occurred specifically in midguts but not in other tissues of females and larvae. A gut-specific defensin gene upregulated by L. major infection, in combination with gut-bacteria, is a promising molecular target for parasite control strategies.

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Population structure and reproductive characteristics of the silky shark Carcharhinus falciformis (Müller & Henle, 1839) (Carcharhiniformes: Carcharhinidae) off the coast of Oaxaca, Mexico

Latin American Journal of Aquatic Research ◽

10.3856/vol44-issue3-fulltext-10 ◽

2017 ◽

Vol 44 (3) ◽

pp. 513-524

Author(s):

María del Carmen Alejo-Plata ◽

Miguel Ángel Ahumada-Sempoal ◽

José Luis Gómez-Márquez ◽

Adrián González-Acosta

Keyword(s):

Population Structure ◽

Sex Ratio ◽

Seasonal Changes ◽

Sexual Maturity ◽

Size Structure ◽

Landing Sites ◽

Silky Shark ◽

Oceanic Species ◽

Carcharhinus Falciformis ◽

Gravid Females

Carcharhinus falciformis is an abundant oceanic species, which occurs in equatorial and tropical zones, with an important catch in the Atlantic and Pacific coasts of Mexico. Samples were taken from December 2000 to December 2007 in four landing sites of the artisanal fleet on the coast of Oaxaca. During the period of study 1236 specimens (602 females and 634 males) of C. falciformis were registered. Total length (TL) ranged from 49 to 217 cm for females (mean = 111.3 cm) and from 59 to 265 cm for males (mean = 111.7 cm). The sex ratio of females to males was 1:1 ( 2 0.05 = 0.78, P > 0.05). The present data suggest a size at first sexual maturity of about 184.8 cm TL for females and 178.5 cm TL for males. The catches were composed mainly of young. In the 52 gravid females examined, the average number of embryos per female was seven; with a range of 3-14 embryos. Mean TL of embryos ranged from 10 to 66 cm with evidence of seasonal changes in the size structure. Results obtained showed that C. falciformis gives birth most of the year, with the highest proportion of births during the rainy season (May to October).

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Environmental Vector Control Practices among Households of Patients with Dengue Fever during the Epidemic of 2018 in Kerala, India

Journal of Evidence Based Medicine and Healthcare ◽

10.18410/jebmh/2021/10 ◽

2021 ◽

Vol 8 (02) ◽

pp. 48-52

Author(s):

Chintha Sujatha ◽

Reshma Rajan Sudha ◽

Sreejith Lalitha Krishnankutty ◽

Prajitha Kannamkottapilly Chandrasekharan

Keyword(s):

Vector Control ◽

Dengue Fever ◽

Protective Factor ◽

Significant Risk ◽

Public Health Problem ◽

Community Level ◽

Control Measures ◽

Major Public Health Problem ◽

Cross Sectional ◽

Breeding Habitats

BACKGROUND Dengue fever is a major public health problem in Kerala. Vector control measures practiced at household level is the most cost-effective way of controlling dengue. This study aims to assess environmental measures of vector control practised among households of suspected or confirmed dengue patients in Thiruvananthapuram district of Kerala. METHODS A cross sectional study was done among households of patients diagnosed with dengue fever and reported in Integrated Disease Surveillance Programme (IDSP) in Thiruvananthapuram district from June to December 2018. Investigators interviewed the household members and made direct observations to collect data on vector control practices using a structured questionnaire. RESULTS A total of 108 houses were surveyed. Potential breeding habitats were found in 58 (53.7 %) houses. Aedes larva was found in containers from four (3.7 %) houses. Dry day observance was not regular with only 5 (4.6 %) houses practicing it weekly. Waste management practiced was proper in 47 (43.5 %) houses. Community level pre monsoon preparedness for epidemics was done in the vicinity of 53 (49.1 %) houses and it was found to be a protective factor against presence of breeding habitats in and around houses (p = 0.013). Low education (p = 0.012) and low occupational status (p = 0.017) were found to be significant risk factors. CONCLUSIONS Even during an epidemic, with occurrence of infections in the family, only half of the households are practising adequate vector control methods. Community level interventions and targeted information education campaign will help improve practice of environmental methods of vector control in dengue. KEYWORDS Dengue, Vector Control, Aedes Control, Environmental Methods, Community Interventions

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Long-lasting microbial larvicides for controlling insecticide resistant and outdoor transmitting vectors: a cost-effective supplement for malaria interventions

Infectious Diseases of Poverty ◽

10.1186/s40249-020-00767-3 ◽

2020 ◽

Vol 9 (1) ◽

Author(s):

Guofa Zhou ◽

Eugenia Lo ◽

Andrew K. Githeko ◽

Yaw A. Afrane ◽

Guiyun Yan

Keyword(s):

Cost Effectiveness ◽

Vector Control ◽

Malaria Vector ◽

Indoor Residual Spraying ◽

Cost Effective ◽

Control Measures ◽

Malaria Vector Control ◽

Potential Cost ◽

Outdoor Transmission ◽

Indoor And Outdoor

AbstractThe issues of pyrethroid resistance and outdoor malaria parasite transmission have prompted the WHO to call for the development and adoption of viable alternative vector control methods. Larval source management is one of the core malaria vector interventions recommended by the Ministry of Health in many African countries, but it is rarely implemented due to concerns on its cost-effectiveness. New long-lasting microbial larvicide can be a promising cost-effective supplement to current vector control and elimination methods because microbial larvicide uses killing mechanisms different from pyrethroids and other chemical insecticides. It has been shown to be effective in reducing the overall vector abundance and thus both indoor and outdoor transmission. In our opinion, the long-lasting formulation can potentially reduce the cost of larvicide field application, and should be evaluated for its cost-effectiveness, resistance development, and impact on non-target organisms when integrating with other malaria vector control measures. In this opinion, we highlight that long-lasting microbial larvicide can be a potential cost-effective product that complements current front-line long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) programs for malaria control and elimination. Microbial larviciding targets immature mosquitoes, reduces both indoor and outdoor transmission and is not affected by vector resistance to synthetic insecticides. This control method is a shift from the conventional LLINs and IRS programs that mainly target indoor-biting and resting adult mosquitoes.

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Reproduction, Growth and Mortality of Venus Striatula (Da Costa) in Kames Bay, Millport

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315400001648 ◽

1961 ◽

Vol 41 (1) ◽

pp. 191-215 ◽

Cited By ~ 52

Author(s):

Alan D. Ansell

Keyword(s):

Sex Ratio ◽

Microscopic Examination ◽

Seasonal Changes ◽

One Year

Seasonal changes in the gonads of both sexes of Venus striatula were followed by macroscopic and microscopic examination, in over 700 animals from a population consisting mainly of one year-group. The sex ratio was approximately equal, and no hermaphrodite adults were found.

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