Nipah Virus: A Zoonotic Virus Transmitted from Bats and Pigs, Causing an Epidemic in Southeast Asia

Nipah Virus (NiV), a member of the Paramyxoviridae family, is one of the most infectious zoonotic viruses in Southeast Asia. First recorded in Malaysia in 1998, the NiV outbreak infected hundreds of people, with an almost 50% death rate. The virus is transmitted through direct contact with contaminated subjects and infecting the human respiratory system. Ephrin B2 and B3, the surface glycoproteins on the host cell, have been the primary and the most effective route for viral entrance. Binding with viral surface G protein, the F protein triggers, enabling viral-host fusion. Until now, NiV vaccines are not yet available in the public market, however, preventions such as avoiding direct contact and masking are advised.

Human cystic echinococcosis:epidemiologic,zoonotic,clinical,diagnostic and therapeutic aspects

This review represents an updated scenario on the transmission cycle,epidemiology,clinical features and pathogenicity,diagnosis and treatment,and prevention and control measures of a cestode parasite Echincoccus granulosus(E.granulosus) infection causing cystic echinococcosis (CE) in humans.Human CE is a serious life-threatening neglected zoonotic disease that occurs in both developing and developed countries,and is recognized as a major public health problem. The life cycle of E.granulosus involves a definitive host(dogs and other canids) for the adult E.granulosus that resides in the intestine,and an intermediate host(sheep and other herbivores) for the tissue-invading metacestode(larval) stage.Humans are only incidentally infected;since the completion of the life cycle of E.granulosus depends on carnivores feeding on herbivores bearing hydatid cysts with viable protoscoleces,humans represent usually the dead end for the parasite.On ingestion of E.granulosus eggs,hydatid cysts are formed mostly in liver and lungs, and occasionally in other organs of human body,which are considered as uncommon sites of localization of hydatid cysts.The diagnosis of extrahepatic echinococcal disease is more accurate today because of the availability of new imaging techniques,and the current treatments include surgery and percutaneous drainage,and chemotherapy(albendazole and mebendazole).But.the wild animals that involve in sylvatic cycle may overlap and interact with the domestic sheepdog cycle,and thus complicating the control efforts.The updated facts and phenomena regarding human and animal CE presented herein are due to the web search of SCI and non-SCI journals.

Zoonotic origins of human coronavirus 2019(HCoV-19/SARS-CoV-2):why is this work important?

The ongoing pandemic of coronavirus disease 2019 (COVID-19), caused by infection with human coronavirus 2019 (HCoV-19/SARS-CoV-2/2019-nCoV), is a global threat to the human population. Here, we briefly summarize the available data for the zoonotic origins of HCoV-19, with reference to the other two epidemics of highly virulent coronaviruses, SARSCoV and MERS-CoV, which cause severe pneumonia in humans. We propose to intensify future efforts for tracing the origins of HCoV-19, which is a very important scientific question for the control and prevention of the pandemic.

Forecasting the number of zoonotic cutaneous leishmaniasis cases in south of Fars province, Iran using seasonal ARIMA time series method

Objective: To predict the trend of cutaneous leishmaniasis and assess the relationship between the disease trend and weather variables in south of Fars province using Seasonal Autoregressive Integrated Moving Average(SARIMA) model,Methods: The trend of cutaneous leishmaniasis was predicted using Mini tab software and SARIMA model,Besides,information about the disease and weather conditions was collected monthly based on time series design during January 2010 to March 2016,Moreover,various SARIMA models were assessed and the best one was selected,Then,the model's fitness was evaluated based on normality of the residuals' distribution,correspondence between the fitted and real amounts,and calculation of Akaike Information Criteria(AIC) and Bayesian Information Criteria(BIC),Results: The study results indicated that SARIMA model(4,1,4)(0,1,0)(12) in general and SARIMA model(4,1,4)(0,1,1)(12) in below and above 15 years age groups could appropriately predict the disease trend in the study area,Moreover,temperature with a three-month delay(lag3) increased the disease trend,rainfall with a four-month delay(lag4) decreased the disease trend,and rainfall with a nine-month delay(lag9) increased the disease trend,Conclusions: Based on the results,leishmaniasis follows a descending trend in the study area in case drought condition continues,SARIMA models can suitably measure the disease trend,and the disease follows a seasonal trend.

The 2019 novel coronavirus disease(COVID-19) pandemic: A zoonotic prospective

Severe acute respiratory syndrome coronavirus 2(SARS-CoV-2),a novel coronavirus(CoV),has recently emerged as a significant pathogen for humans and the cause for the recent outbreak of the 2019 novel coronavirus disease(COVID-19)throughout the globe.For developing any preventive measure,an understanding of the zoonotic pattern for this virus is a necessity.We should have a clear knowledge of its reservoir host,its distribution pattern and spreading routes.Information about zoonotic reservoirs and its transmission among them can help to understand the COVID-19 outbreaks.In this article,we discuss about the bats as the zoonotic reservoir of several CoV strains,co-existence of bats and CoV/viruses,the sequence similarity of SARS-CoV-2 with bat SARS-like CoV,the probable source of the origin of SARS-CoV-2 strain and COVID-19 outbreak,intermediate host of CoVs and SARS-CoV-2,human to human transmission and the possibility to maintain the zoonotic barriers.Our knowledge about the zoonotic reservoir of SARS-CoV-2 and its transmission ability may help develop the preventive measures and control for the future outbreak of CoV.

Quantification of Zoonotic Bacterial Pathogens within Commercial Poultry Processing Water Samples Using Droplet Digital PCR

Raw poultry and poultry products are a significant source of zoonotic bacterial pathogen transmission;thus the sensitive detection of major zoonotic pathogens (Salmonella spp., Campylobacter jejuni, and Listeria monocytogenes) is a vital food safety issue. Recently, third generation PCR technology, known as droplet digital PCR (ddPCR) has been developed to be more accurate and sensitive to detect genetic targets than current quantification methods, but this technology has not been tested within an industrial setting. There is an on-going study within our laboratory is investigating the effects of sampling times and sampling methods on the cultural and molecular (via qPCR) quantification of dominant zoonotic pathogens within a poultry processing facility. This presents a unique opportunity to compare the quantification resulted from this emerging, third generation technology to traditional quantification methods currently employed by the poultry industry. The results show that ddPCR detected pathogen-specific genes from more pathogen:sampling time combinations than either the qPCR or culturing methods from the final scalder and chiller tanks at three stages of processing (Start, Mid, and End). In fact, both ddPCR and qPCR substantially outperformed culture methods commonly used in poultry processing food safety-related studies, with Salmonella recovered only from the Mid and End sampling times from the scalder tank. While neither C. jejuni nor L. monocytogenes were recovered culturally, ddPCR was able to detect their respective genes commonly throughout the processing day in both the scalder and chiller water samples. Additionally, the use of unfiltered processing water provided significantly greater detection of bacterial and pathogen-specific gene abundances than did an analysis of larger volumes of filtered water. Considering the ddPCR-derived concentrations of the bacterial pathogens were consistent with what was previously found culturally in commercial poultry processing operations, ddPCR represented a significant advancement in poultry processing zoonotic pathogen quantification.

A survey of zoonotic diseases in trade cattle slaughtered at Tanga city abattoir:a cause of public health concern

Objective:To estimate the prevalence of hydatidosis,cysticercosis,tuberculosis,leptospirosis,brucellosis and toxoplasmosis in slaughtered bovine stock(aged≥3 years)at Tanga city abattoir,Tanzania.Methods:Prevalence estimation of the five zoonotic diseases was undertaken through an active abattoir and sero-survey was carried out in Tanga city,during the period of January 2002and March 2004.Serum samples collected from a sub-sample(n=51)of the slaughter stock were serologically screened for antibodies against brucellosis,leptospirosis and toxoplasmosis using Rose Bengal plate test,microscopic agglutination test(for 5 serovars of Leptospira interrogans)and Eiken latex agglutination test,respectively.The same animals were tested for tuberculosis using the single intradermal tuberculin test.Results:Post mortem examination of 12 444 slaughter cattle(10 790 short horn zebu and 1 654 graded)over a period of twenty two months,showed a prevalence of 1.56%(194)for hydatidosis,1.49%(185)for cysticercosis and 0.32%(40)for tuberculosis.In all three zoonoses,a statistically significant difference in infection rates was noted between the short horn zebu and graded breeds(P<0.05).The overall seroprevalences of animals with brucellosis,toxoplasmosis and leptospirosis antibodies were found to be 12%,12%and 51%,respectively.The most common leptospiral antibodies detected were those against antigens of serovars Leptospira hardjo(29%),Leptospira tarassovi(18%),Leptospira bataviae(4%)and Leptospira pomona(0%).With regard to tuberculosis,10%(n=5)of the animals tested were classified as non-specific reactors or inconclusive.Conclusions:The study findings suggest that brucellosis,toxoplasmosis and leptospirosis are prevalent in Tanga and provide definitive evidence of slaughtered stock exposure to these zoonotic agents with concurrent public health consequences.

Molecular characterization of sandflies and Leishmania detection in main vector of zoonotic cutaneous leishmaniasis in Abarkouh district of Yazd province,Iran

Ohjective:To assess molecular characterization,distribution,seasonal activities of sandfly species and Leishmania parasites infecting them for this zoonotic cutaneous leishmaniasis focus.Methods:The collections were carried out in 2009-2011 using CDC traps,Sticky Papers and manual aspirator in and around the villages in Abarkouh district.Individual sandflies were characterized by PCR amplification and sequencing of fragments of their mitochondrial cytochrome b gene.Leishmania parasite infections within sandflies were performed by targeting Cyt b,ITS-rDNA,k-DNA and microsatellite genes.Results:The PCR assays detected only Leishmania major(L.major).All infections(30)were found in the abundant and widespread vector Phlebolomus papalasi(P.papatasi).Small numbers of other sandfly species were also screened for infections,but none was found.Sergentomyia sinloni and P.papalasi were the predominant members in all locations of this district and in all habitats throughout the trapping season.Only five other sandfly species were found,namely Phlebolomus ansari,Phlebotomus caucasicus,Phlebotomus sergenti,Sergentomyia dentata and Sergentomyia merviney.Conclusions:In the current survey,the only infections detected are of L.major in females of P.papatasi(30 out of190).The rates of infection of P.papalasi by L.major are not significantly different in compare with other locations in Iran with no diversity of parasite strains.Zoonotic cutaneous leishmaniasis may have emerged only recently in Abarkouh district,and the reason may well be the instability of the transmission cycles there.

Preliminary study on investigation of zoonotic visceral leishmaniasis in endemic foci of Ethiopia by detecting Leishmania infections in rodents

Objective:To investigate the zoonotic visceral leishmaniasis(ZVL) by identification of the most probable reservoir hosts using parasite isolation and analysis of a possible transmission dynamics of the disease in extra-domestic agricultural fields and rural villages.Methods:Rodents were collected from selected study sites in kala-azar endemic areas based on information for localities of kala-azar cases for screening of Leshmania infections using parasitological,serological and polymerase chain reaction(PCR) from March.2013 to January,2014.Ketamine(Clorketam Veterinary) was used to anaesthesize the rodents according the prescribed dosage(average 2 mg/kg for intra-venous route).The blood obtained using sterile needle was dropped into sterile filter paper and allowed to air dry before sealing in plastic bags.The tissues from liver,spleen and skin were macerated in Locke's solution before transferring them into NNN medium.Blood and touch smears of liver,spleen,skin and bone marrow were prepared for fixing using methanol and staining by Giemsa stain for microscopy.These tissues were also ascd for DNA extractions and PCR amplification of Leishmania infection.Results:A total of 335 rodents(13 species) were analyzed by sampling internal organs.The infection rate by PCR was 11.1%(6/54) for Arvicanthis nilothicas compared to 17.6%(3/17) and 12.5%(2/16) for Acomys cahirinus and Tarera(C) robustus respectively.Almost all the infections were found from bone marrow samples(8/48 or 16.7%) compared with 1/91(1.1%) liver,2/87(2.2%) spleen and 0/87(0%) skin.In all study sites with past human VL cases,rodents and proved vectors shared similar habitats.Conclusions:Leishmania donovani might circulate among different species of rodents in kala-azar endemic lowlands and valleys of Ethiopia by Phlebotamus orientalis and Phlebotomus martini.Detailed studies to substantiate the preliminary data on the possible role of these rodents arc urgently needed.

Genomic characterization of velogenic avian orthoavulavirus 1 isolates from poultry workers: Implications to emergence and its zoonotic potential towards public health

Objective:To carry out the genetic characterization and evolutionary analysis of three avian orthoavulavirus 1(AOAV-1)isolates from poultry workers with respiratory symptoms.Methods:Using Illumina Mi Seq,whole-genome sequencing was carried out to assess the evolutionary dynamics of three AOAV-1 isolates.A phylogenetic and comparative analysis of all coding genes was done using bioinformatics tools.Results:Phylogenetic analysis and genetic distance estimation suggested a close relationship among human-and avian-originated velogenic strains of genotypeⅩⅢ,sub-genotypeⅩⅢ.2.1.Several substitutions in the significant structural and biological motifs were exclusively identified in the human-originated strains.Conclusions:To our knowledge,this is the first report of a velogenic AOAV-1 isolate from natural infection of the human upper respiratory tract.Our findings highlight the evolution and zoonotic potential of velogenic AOAV-1 in a disease endemic setting.

Epizootic, Endemic and Pandemic Zoonotic Viral Infections

More than 60% human infectious diseases have zoonotic origin. Cross species transmission of pathogens is a continuous, dynamic process that occurs throughout the world, giving rise to epizootic (temporary, limited infection), endemic (on-going infection limited to a defined geographic region) and pandemic viral infections (infection spreading to every part of the world) like the current COVID-19 pandemic, which depends on the existing conditions on the ground. In Nov 2021, sudden mortality of numerous migrating demoiselle cranes was reported from their resting site near Jodhpur, Rajasthan. The symptomatic cranes became gradually weak and were unable to fly. They eventually fell dead which caused concern locally, given the current prevailing SARS-CoV-2 pandemic situation the world over. By the end of Dec 2021, the number of cranes with mortality and morbidity reduced, making it a temporary “epizootic infection”. Molecular diagnosis carried out at a specialized laboratory identified the etiological agent to be the highly pathogenic Avian Influenza Virus H5N1 (HPAIV), which has been responsible for morbidity of avian species from different parts of the world. There was no report of spreading the H5N1 AIV infection from the infected migratory cranes to nearby chicken farms or pig farms for now. In the absence of vaccines against the highly pathogenic H5N1 AIVs, and the inherent ability of influenza viruses, both avian AIV and human IAVs to constantly mutate its envelope gene or the surface antigens, resulting from the error-prone nature of the viral RNA Polymerase enzyme are the roadblocks for development of a universal, broad-spectrum influenza vaccine. Even when such a universal vaccine against H5N1 is available, vaccinating a large number of wild migratory cranes would be difficult. However, it is possible and indeed necessary to vaccinate chickens in poultry farms and pigs in farms that raise pigs for human consumption.

Unveiling the Threat: Case Reports of Extra-Pulmonary Tuberculosis among Sanctuary Chimpanzees

Primate sanctuaries across Africa play a pivotal role in the rescue and rehabilitation of confiscated and rescued wild primates, many of whom have had extensive contact with humans prior to their arrival and throughout the rehabilitation process, heightening the risk of disease transmission. While tuberculosis is not naturally occurring in free-living chimpanzees, it has been extensively observed in captive primates that have been in close proximity to humans or other captive primates infected with Mycobacterium tuberculosis. This case report delves into an outbreak of extra-pulmonary tuberculosis among juvenile chimpanzees within a sanctuary, detailing the associated diagnostic challenges and treatment approaches. The five cases had close contact with a caregiver infected with tuberculosis, subsequently transmitting the infection to other in-contact chimpanzees. Prolonged treatment, employing the human protocol of quadri-therapy (rifampicin, isoniazid, pyrazinamide, and ethambutol), followed by bi-therapy (rifampicin and isoniazid), resulted in complete resolution for all five cases. These cases underscore the critical importance of maintaining high levels of biosecurity, implementing effective quarantine measures, and adhering to strict hygiene practices when working with non-human primates.

Nipah Virus Unveiled: A Review Article

Nipah virus (NiV) is a highly infectious zoonotic pathogen that poses a significant threat to human and animal health. First identified in Malaysia in 1998, NiV has since caused several outbreaks in Southeast Asia, with sporadic cases reported in Bangladesh and India. The virus is primarily transmitted to humans through direct contact with infected animals, primarily fruit bats, or through the consumption of contaminated fruits and their juices. NiV infection presents a wide spectrum of clinical features, ranging from mild respiratory illness to severe encephalitis, with a high case fatality rate. The incubation period typically ranges from 4 to 14 days, during which patients develop fever, headache, myalgia, and respiratory symptoms such as cough and sore throat. As the disease progresses, neurological signs become prominent, including altered consciousness, seizures, and focal deficits. Severe cases may exhibit acute respiratory distress syndrome and multi organ failure. Laboratory findings often include lymphocytopenia, thrombocytopenia, and elevated liver enzymes. Diagnosis of NiV infection requires specialized laboratory testing, including reverse transcription-polymerase chain reaction (RT-PCR) and serological assays. Currently, no specific antiviral treatment exists for NiV infection, and management primarily focuses on supportive care. Prevention and control strategies encompass public health interventions, surveillance, and raising awareness among healthcare providers and the general population. The emergence and re-emergence of NiV highlight the urgent need for continued research, improved diagnostic capabilities, and the development of effective vaccines and therapeutics to mitigate the impact of this deadly virus.

Establishment of an indicator framework for the transmission risk of the mountain-type zoonotic visceral leishmaniasis based on the Delphi-entropy weight method

Background: Visceral leishmaniasis (VL) is one of the most important neglected tropical diseases. Although VL was controlled in several regions of China during the last century, the mountain-type zoonotic visceral leishmaniasis (MT-ZVL) has reemerged in the hilly areas of China in recent decades. The purpose of this study was to construct an indicator framework for assessing the risk of the MT-ZVL in China, and to provide guidance for preventing disease.Methods: Based on a literature review and expert interview, a 3-level indicator framework was initially established in November 2021, and 28 experts were selected to perform two rounds of consultation using the Delphi method. The comprehensive weight of the tertiary indicators was determined by the Delphi and the entropy weight methods.Results: Two rounds of Delphi consultation were conducted. Four primary indicators, 11 secondary indicators, and 35 tertiary indicators were identified. The Delphi-entropy weight method was performed to calculate the comprehensive weight of the tertiary indicators. The normalized weights of the primary indicators were 0.268, 0.261, 0.242, and 0.229, respectively, for biological factors, interventions, environmental factors, and social factors. The normalized weights of the top four secondary indicators were 0.122, 0.120, 0.098, and 0.096, respectively, for climatic features, geographical features, sandflies, and dogs. Among the tertiary indicators, the top four normalized comprehensive weights were the population density of sandflies (0.076), topography (0.057), the population density of dogs, including tethering (0.056), and use of bed nets or other protective measures (0.056).Conclusions: An indicator framework of transmission risk assessment for MT-ZVL was established using the Delphientropy weight method. The framework provides a practical tool to evaluate transmission risk in endemic areas.

Zoonotic parasites carried by invasive alien species in China

Background:The invasive alien species may lead to great environmental and economic crisis due to its strong capability of occupying the biological niche of native species and altering the ecosystem of the invaded area.However,its potential to serve as the vectors of some specific zoonotic pathogens,especially parasites,has been neglected.Thus,the damage that it may cause has been hugely underestimated in this aspect,which is actually an important public health problem.This paper aims to discuss the current status of zoonotic parasites carried by invasive alien species in China.Main body:This review summarizes the reported zoonotic parasites carried by invasive alien species in China based on the Database of Invasive Alien Species in China.We summarize their prevalence,threat to human health,related reported cases,and the roles of invasive alien species in the life cycle of these parasites,and the invasion history of some invasive alien species.Furthermore,we sum up the current state of prevention and control of invasive alien species in China,and discuss about the urgency and several feasible strategies for the prevention and control of these zoonoses under the background of booming international communications and inevitable globalization.Conclusions:Information of the zoonotic parasites carried by invasive alien species neither in China or worldwide,especially related case reports,is limited due to a long-time neglection and lack of monitoring.The underestimation of their damage requires more attention to the monitoring and control and compulsory measures should be taken to control the invasive alien species carrying zoonotic parasites.

Fruit bats as anatural reservoir of zoonotic viruses

As a natural reservoir of manifold zoonotic viruses, fruit bats have been involved in at least three emerging zoonoses in recent years. This paper aims to intro-duce the epidemiological characteristics of these diseases emerged in the Australasian region between 1994 and 1999, transmission pathways of the newly discovered viruses and the relationship between the changed entironment of fruit bats and occurrences of these emerging diseases and provide a clue for the epidemiological investigations of SARS.

Mathematical modelling for Zoonotic Visceral Leishmaniasis dynamics:A new analysis considering updated parameters and notified human Brazilian data

Brazil is one of the highest endemic countries for Zoonotic Visceral Leishmaniasis:according to the Brazilian Ministry of Health,the annual number of new human cases and deaths due to this disease has been increasing for the last 20 years.In addition,regarding the Americas,the specific relationship between canine and human for Visceral Leishmaniasis dynamics is still not well understood.In this work we propose a new model for Zoonotic Visceral Leishmaniasis,based on the models previously published by Burattini et al.(1998)and Ribas et al.(2013).Herein,we modeled the disease dynamics using a modified set of differential equations from those two authors,considering the same assumptions(inclusion of human,dog and sandfly populations,all constants over time).From this set of equations we were able to calculate the basic reproduction number R 0 and to analyze the stability and sensitivity of the system to the parameters variability.As main result,when the stability of the system is reached,the normalized reporting human cases rate is estimated in 9.12E-08/day.This estimation is very close to the 2015 report from Araçatuba city,5.69E-08/day.We also observed from stability and sensitivity analysis that the activity of sandfly population is critical to introduction and maintenance of Zoonotic Visceral Leishmaniasis in the population.In addition,the importance of dog as source of infection concentrates on latent dog,since it does not show clinical symptoms and signs and,therefore,has a great contribution to disease dissemination.As conclusion,considering the presently ethical issues regarding to elimination of positive dog in Brazil and the highly sensitivity of disease dynamics on sandfly population,we recommend that the sandfly population control should be prioritized.

A relatively high zoonotic trematode prevalence in Orientogalba ollula and the developmental characteristics of isolated trematodes by experimental infection in the animal model

Background:Food-borne parasitic diseases decrease food safety and threaten public health.The snail species is an intermediate host for numerous human parasitic trematodes.Orientogalba ollula has been reported as intermediate hosts of many zoonotic trematodes.Here,we investigated the prevalence of zoonotic trematodes withinO.ollula in Guangxi,China,and assessed their zoonotic potential.Methods:Snails were collected from 54 sites in 9 cities throughout Guangxi.The snail and trematode larvae species were determined by combining morphological characteristics and molecular markers.The trematodes prevalence and constituent ratio were calculated and compared among different habitat environments.Phylogenetic trees of the trematode species were constructed using the neighbor-joining method with nuclear internal transcribed spacer 2(ITS2)sequences.The developmental cycles of the isolated trematodes were examined by experimental infection in ducks.The developmental characteristics ofEchinostoma revolutum was recorded by dissecting infected ducklings from 1-day post infection(dpi)to 10 dpi.Results:The overall prevalence of trematode larvae was 22.1%(1818/8238)inO.ollula from 11 sample sites.Morphological together with molecular identification,showed thatE.revolutum,Australapatemon sp.,Hypoderaeum conoideum,Pharyngostomum cordatum,andEchinostoma sp.parasitizedO.ollula,with the highest infection rate ofE.revolutum(13.0%).However,noFasciola larvae were detected.The trematodes prevalence and constituent ratio varied in two sub-biotypes(P<0.01).A neighbor-joining tree analysis of ITS2 sequences resulted in distinct monophyletic clades supported by sequences from isolated larvae with high bootstrap values.Ducklings exposed toO.ollula infected withEchinostoma sp.,E.revolutum,andH.conoideum larvae were successfully infected.The animal model forEchinostoma revolutum was successfully established.E.revolutum matured from larvae to adult at 10 dpi in the intestine of the duck,and the developmental characteristics ofE.revolutum were characterized by the maturation of the reproductive and digestive organs at 6-8 dpi.Conclusions:This study revealed a high prevalence of zoonotic trematodes inO.ollula from Guangxi,China.Existing trematodes infection in animals and human clinical cases,coupled with the wide geographical distribution ofO.ollula,necessitate further evaluations of the potential risk of spillover of zoonotic infection from animal to human and vice versa.

Mathematical analysis of a model for zoonotic visceral leishmaniasis

Zoonotic visceral leishmaniasis(ZVL),caused by the protozoan parasite Leishmania infantum and transmitted to humans and reservoirhosts by female sandflies,is endemic inmany parts of the world(notably in Africa,Asia and the Mediterranean).This study presents a new mathematical model for assessing the transmission dynamics of ZVL in human and non-human animal reservoir populations.The model undergoes the usual phenomenon of backward bifurcation exhibited by similar vector-borne disease transmission models.In the absence of such phenomenon(which is shown to arise due to the disease-induced mortality in the host populations),the nontrivial disease-free equilibrium of the model is shown to be globallyasymptotically stable when the associated reproduction number of the model is less than unity.Using case and demographic data relevant to ZVL dynamics in Arac atubamunicipality of Brazil,it is shown,for the default case when systemic insecticide-based drugs are not used to treat infected reservoir hosts,that the associated reproduction number of the model (ℛ0) ranges from 0.3 to 1.4,with a mean of ℛ0=0:85.Furthermore,when the effect of such drug treatment is explicitly incorporated in the model(i.e.,accounting for the additional larval and sandfly mortality,following feeding on the treated reservoirs),the range ofℛ0 decreases toℛ02∈[0.1,0.6],with a mean ofℛ0=0:35(this significantly increases the prospect of the effective control or eliminationof the disease).Thus,ZVL transmissionmodels(in communities where such treatment strategy is implemented)that do not explicitly incorporate the effect of such treatmentmay be over-estimating the disease burden(asmeasured in terms ofℛ0)in the community.It is shown thatℛ0 ismore sensitive to increases in sandflylifespanthan thatof the animal reservoir(so,a strategy that focuses on reducing sandflies,rather than the animal reservoir(e.g.,via culling),may be more effective in reducing ZVL burden in the community).Further sensitivity analysis of themodel ranks the sandfly removal rate(by natural death or by feeding from insecticide-treated reservoir hosts),the biting rate of sandflies on the reservoir hosts and the progression rate of exposed reservoirs to active ZVL as the three parameters with themost effect on the disease dynamics or burden(as measured in terms of the reproduction number ℛ0).Hence,this study identifies the key parameters that play a key role on the disease dynamics,and thereby contributing in the design of effective control strategies(that target the identified parameters).

Vaccination of a multi-group model of zoonotic diseases with direct and indirect transmission

Vaccination plays an important role in preventing or reducing the spread of zoonotic diseases.In this paper,we develop a susceptible-vaecinated-exposed-infectious-pathogen multi-group epidemic model of zoonotic diseases incorporating nonlinear direct and indi rect incidence rates,nonlinear pathogen shedding rates,and common environmental contamination.Under certain assumptions,we first obtained the basic reproduction number of the model.Then,we utilized the comparison principle and global Lyapunov function method to prove global stability of dynamical equilibria.Finally,we analyzed optimal vaccination strategy.All the theoretical predictions were verified by numerical simulations.