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Challenge for Veterinarians-Emerging and Re-emerging Zoonoses

Asif Iqbal A. K.Tripati Najimaana
Vol 2(10, 82-92

Emergent disease episodes have increased globally and served as reminder of the existence of infectious diseases. They have been an important part of human life due to their influence on human biology, sociology and even determine the course of major historical events. With the world becoming a smaller place to live in, exotic pets and wild animals becoming more accessible, the risk of human being exposed to additional diseases is possible. Furthermore, there have been threats of new diseases during the past two decades due to the evolution and adaptation of microbes and the re-emergence of old diseases due to the development of antimicrobial resistance and their capacity to spread to new geographic areas. Considering the fact that most of the emerging diseases are often zoonotic in nature, the significance of zoonoses in the emergence of human infections cannot be overstated. Around 61% human microbial pathogens and 73 % emerging human pathogens identified during the past two decades are zoonotic (Gregar, 2007). Approximately 75 % of disease that have emerged over the past two decades may have a wildlife source (Woolhouse, 2002). Morens et al, 2004, reported that fight against zoonoses starts by eliminating the pathogen at its animal source. So the need to understand disease of animals has become more apparent and which give both opportunity and challenge for the veterinarians as they have both clinical and population medicine training as well as education in disease control. This review of emerging and re-emerging diseases should be of critical importance to microbiologists, clinicians, public health personnel and policy makers in India.

Keywords : Emerging Re-emerging Zoonoses causes control and challenges


The present status of some of the emerging and re-emerging diseases in India has been reviewed until date, but the true prevalence of many such diseases in India is not known. Though poorly documented, emerging and re-emerging zoonotic diseases are major public health problem in India as approximately 80% population in India lives in close contact with domesticated animals and there is also an abundance of vectors.

Chikungunya is no stranger to the Indian sub-continent, since its first isolation in Kolkata, in 1963, there have been several reports of Chikungunya virus infection in different parts of India. Ravi (2006), reviewed the disease in Indian subcontinent, after the last outbreak of Chikungunya virus infection occurred in India in 1971. Subsequently, there has been no active or passive surveillance carried out in the country and therefore, it was presumed that the virus had disappeared from the subcontinent, Pavri (1986). However, recent reports of large scale outbreaks in several parts of Southern India have confirmed the re-emergence of this virus by Centre for disease control (CDC, 2006). During 2007, a total of 56365 suspected cases of Chikungunya fever have been reported from fourteen different states and union territories in India and the state of Kerala alone accounts for 42.7 % of total number cases, the state of West Bengal and Lakshyadeep recorded higher number of cases in 2007 as compared to 2006. Whereas no case was reported from Madahaya Pradesh, Pondichery and islands of Andaman and Nicobar as compared to 2006 when 60132, 542 and 1549 cases were reported, respectively (Mahajan et. al.,2009).

The success of influenza type A virus to maintain it self in the population is well known and is attributed to the ability of the virus to reassort its genetic material by means of genetic shift and drift time after time. According to Schild (1984) disease resembling influenza has been known since 20th centaury long before its identification in 1933 at least three pandemic had occurred viz., 1889-90, 1898-1900 and 1918-19. This influenza type-A virus and its subtypes are knows to cause disease in birds, humans and wide species of wild and domestic animals. The natural reservoir of all types of influenza-A virus is water fowl with pig act as mixing vessel and all other animals act as maintance host. The sub-type H5N1 (Avian flu virus), which has created panic in India in 2005 had been first isolated in Scotland and infect domestic, wild, migratory birds, mammals and human in 36 countries and claimed hundreds of life till date. On the other hand sub-type H1N1 (Swine flu virus) had re-emerged in the form of pandemic in 2009 was caused by new strain of H1N1 known as novel influenza A H1N1 and was first detected in Mexico in March and April 2009 and the first novel H1N1 patient in the United States was confirmed by CDC on April 15, 2009. The new H1N1 strain is formed by the re-assortment of four strains, North American Swine Influenza, North American avian influenza, Human influenza, and Swine Influenza of Asia and Europe (CDC fact 2009). The evidences had suggested that first H1N1 pandemic occurs during 1918-19 and following 70 years, swine influenza strains were exclusively H1N1. Then, between 1997 and 2002, new strains of three different sub-types and five different geno-type emerged as cause of influenza among pigs in North America. H3N2 emerged in1997-98 and re-assortment between H1N1 and H3N2 produces H1N2. In 1999 H4N6 strain crossed the species barrier from birds to pigs in Canada, but was fortunately confined to single farm.

Plague had caused three pandemics since the 6th century with 12 million deaths alone in India since the first recorded case in 1896 in Bombay (John, 1996). After the last laboratory-confirmed case was reported in 1966 in Karnataka, there was a lull for almost three decades till two outbreaks were reported during August-October in 1994, an outbreak of pneumonic plague in Surat, Gujarat and the second outbreak of bubonic plague in Beed, Maharashtra. There were a total of 54 deaths (52 in Surat) and 876 seropositive cases; 596 in Maharashtra, 151 in Gujarat, 68 in Delhi, 50 in Karnataka, 10 in Uttar Pradesh and 1 in Madhya Pradesh. Gupta and Sharma (2007) reported an outbreak of 16 confirmed cases of pneumonic plague seen during 2002 in Himachal Pradesh.

The last decade of the 20th century witnessed a sharp increase in the global re-emergence of cholera, in September 1992, V. cholerae O139 Bengal (the first non-O1) appeared in south India. This genome of V. cholerae is in a state of constant flux, resulting in the reemergence and displacement of serotypes. Narang et al (2008) described the changing patterns of V. cholerae in Maharashtra during 1990–2005. Das and Gupta (2005) reported the diversity of V. cholerae isolated in Delhi during 1992–2000.

Leptospirosis is re-emerging as important public health problem in India. Seghal (2006) has reviewed the epidemiological pattern of disease in India and the sero-prevalence is reported to be high (52.7%) among high-risk population of these Islands and 19.8% and 9.3% in Madras and Bangalore respectively. Outbreaks were reported from Mysore, Gujarat, Nagpur and Andamans in 1997. There was a severe outbreak in Mumbai in May 2000 and Kerala in August 2000, causing significant mortality( Mahajan et. al., 2008). An outbreak reporting 102 cases in Mumbai following prolonged water logging due to heavy rainfall during July, 2002. (WHO 2006).


Brucellosis is primarily a disease of animals and is occupational hazard to man. During the last 10 years a conciderable increase in infection has been recorded among the human population, (Sherikar, 2006). Mathur (1964) from north India reported seroprevalence of 8.5% among dairy workers and 4.2% in aborted women. Thakur and Thapliyal (2002) reported a seroprevalence of 17.39% in field veterinarians and abattoir workers. Seropositive cases were seen in 28 of 414 (7.0%) patients of patients of pyrexia of unknown origin (PUO) in Varanasi (Sen et al.,2002) and 28 of 3532 (0.8%)) in Kashmir (Kadri et al., 2000). Mantur et al (2007) have reported seroprevalence of 1.6% by standard agglutination test (> 1:160) and isolated B. melitensis in 43 pediatric patients during a period of 13 years in Karnataka. Agasthya et al (2007) examined 618 sera from various professionals at risk and 15.69% tested positive. These studies clearly show a high prevalence of the disease in occupational exposed groups in India.

Table 1:-Important zoonotic diseases with reasons of emergence and re-emergence


Name of disease




Transmission /vector







Possible reason of emergence and re-emergence

Chikungunya fever



of togaviridae


Mosquito       ( Aedes)

Human, non human primates, other mammals, birds  


human primates

Africa, South east Asia,

Indian ocean


Domestication of pathogen and vector.

Urbanization and expansion.





of   flaviviridae


Mosquito       ( Aedes)


Human, non human primates



human primates




Adaptation and urbanization of vector.

Ineffective vector control






Ebola virus of filoviridae





Humans, animals and non-human primates


Non human primates and bats




Hunting and butchering
Illegal global transport of non human primates.
Alteration of natural fauna.
Hanta virus plumonary syndrome (HPS) Hantavirus Direct – droplet infection Human, rodents, animals. Wild rodents Forest exploration.

Deforestation, expansion and settlements along forest edges.


Hydatid disease


Eccinococcus multiocularis





Small mammals.


Rodents and foxes




Increase in rodent and fox hosts.
Human expansion into forest, exposure of susceptible population







Sand fly   Phlebotomus


Humans, domestic and wild animals.




South America.

Human expansion into forest
Domestication of zoophilic vectors
Domestication of zoonotic cycles by non-immune workers.


Spirochaetes of species Leptospira Direct and Indirect contact Humans, animals, birds and rodents.  





Watershed alteration and flooding


Lyme disease

Borrelia burgdoferi Ticks

( ixodes)





Possible association with deforestation and habitat fragmentation
Marburg haemorragic fever RNA- virus of Filoviridae Direct contact Humans and non human primates Non human primates  


Hunting and butchering of wild animals.

Forest exploration.

Oropouche fever Orthobunya virus of bunyaviridae Mosquito and biting midges Non-human primates


South America Forest travel.
Vector composition changes
Porcine respiratory and encephalitis syndrone (PRES)  




Direct contact

Pigs, human, dog, horses, goats, rodents  

Fruit bats


South Asia

Pig farming near forest edges.

Fruit production on forest borders.


Rift valley fever



Mosquito     ( Aedes and culex ) Human, cattle, sheep, rodents, birds.  




Rearing of sheep near forests.

Urbanization and expansion of vector.

Rockey mountain spotted fever  

Rickettsia rickettsii



( Ixodid )

Humans and other mammals, Dogs, wild rodents North America Forest recreation.

Human expansion into forest.







Humans, animals and Non-human primates bats
and Civets



Southeast Asia

Harvesting, marketing and mixing of bats and civet cats.
Wildlife trade for human consumption

Simian immuno-deficiency virus


Lentivirus of retroviridae



Humans, animals and Non-human primates  

Non-human primates




Hunting and butchering of wildlife.
Pathogen adaptation.

Sleeping sickness


and T.gambisane

Tse-tse fly (glossina) Humans, cattle’s, and wild animals Wild game animals West and Central Africa Human expansion disease incidence associated with forest.

West Nile fever


Flavivirus of flaviviridae




Birds, humans and animals


Wild birds

Asia, Africa, Middle East and Europe Adaptation and urbanization of vector.

Ineffective vector control.


Yellow fever




Mosquito       ( Aedes)

Human, non human primates Nonhuman primates Africa, South America Deforestation and

Urbanization of vector and pathogen.

Listerosis is an emerging zoonotic disease that is responsible for 28% deaths due to food borne illnesses in the United States, but in India, very few studies have been done and the data is not well established. Bhujwala et al, in 1970 reported L monocytogenes in cervical secretions of 1.3-3% of cases with bad obstetrical history but none of the 125 samples of cerebrospinal fluid obtained from cases of meningitis were positive. Thomas et al (1981) in a prospective study of 1300 newborns found the pathogen in only two cases.

Campylobacter species are the most common cause of neonatal diarrhea in India, Jain et al (2005) reported isolation of C. jejuni in 13.5% of the diarrhoea patients and this was more frequent than combined Salmonella and Shigella infections (4.3%; P < 0.001). Intoxication caused by emerging E.coli 0157 (Escherichia coli) and Salmonella are major health problems in children’s near more industrialized areas (Sherikar et al., 2006). Non-O157 EHEC (Enterohaemmoraghic Escherichia coli) were reported in 1.4% of stools from cases of bloody diarrhoea in Kolkata (Ministry of Health and Welfare 2006). EHEC O157 sorbitol phenotypes have been isolated from the Ganges River, Varanasi by Hamner et al (2007).

Causes and Phenomenon of Disease Emergence

Disease emergence is a transient phenomenon in human population and in its most severe form is typically a consequence of rapid social and environmental changes or instability associated with the globalization, especially the rapidly increasing ease of the transportation, are mixing people, domestic animals, wild life and plants, along with their parasites and pathogens. Deforestation and aforestation often disturbs the equilibrium or natural ‘eco-niche’ or silent foci of the micro   organism for example deforestation in Mysore (Karnataka) and grazing by cattle in these areas led to the emergence of ‘kyasanur forest disease’. Whereas aforestation in United States led to the emergence of ‘lyme disease’ and can be viewed ecologically as an extension of host parasite relationship. These factors are as much part of ecosystem as prey–predator or plant-herbivore relationship. The reasons of some of the major re-emerging or emerging zoontic diseases are described in Table 1. As reveled by best available evidences and information on agents like Nipha virus, EBOLA, Marburg virus, Rift valley fever, West Nile Fever, H5N1 avian influenza, lyme disease and Bovine spongiform encephalopathy can be related with the components which are complex to under stand and leads to emergence or re-emergence of diseases, which includes :-

  • Microbial Determinants:- It involves mechanism at molecular level such as genetic shift and drift, mutation, drug resistance, natural selection.
  • Individual Determinants:- It involves the status of individual immune response.
  • Population Determinants:- It involves behavioral, societal, commercial, transport and iatrogenic factors.
  • Environmental Determinants:- It involves ecological, climatologically and social influence.

Role of Veterinarian

Veterinarians are in unique position to strengthen the countries surveillance system, due to their ideal position in society, easy access to the pet owner public, their knowledge and training. Last but not the least their role in the human animal bond. These professional competencies are essential for identification and management of new emerging zoonoses. Appropriate surveillance, clinical curiosity, epidemiological studies and laboratory training are the essential tools that veterinarians must use to meet the challenge of emerging zoonoses. Thus we and our colleagues greatly enhanced the ability to rapid implementation of preventive measure for emerging zoonoses. Together we can help to better under stand the risk associated with emerging zoonotic diseases and work together to improve the health status of our communities by :-

  • Notification of any suspected or conformed case or outbreak involving a disease of public health importance.
  • Cooperate with public health authorities in the investigation of suspected and confirmed cases of emerging zoonotic disease.
  • Implementation of control measures including isolation and quarantine of animals as per the recommendation of public health authorities.
  • Collection of data from pet owners, zoo, wildlife parks, dispensaries, private clinics and disperse them to the concerned and needful authorities.
  • Educating and counseling of pet owners regarding the zoonotic aspect of the disease, their control, diagnosis, prophylactic measures and treatment etc.

Challenges With Respect To India

  • Poor public health infra structure to face emerging and re-emerging zoonoses.
  • Public health initiatives on control of zoonoses have failed to focus on community participation, socio-economic benefits with little or no veterinary inputs.
  • Surveillance programs on zoonoses lack co-ordination between national, regional, local human data base.
  • Ecological, ethological, social, ethical and psychological consideration in zoonoses control and food safety programs have not been addressed adequately.
  • There is absolutely no or very little infra structure for handling unforeseen emergencies following natural disaster

Control and Prevention

In view of the enormous impact of emerging zoonoses on human and economic development, collaboration between the public health sector, agriculture, veterinary and concern authorities is required to develop policies and practices for the prevention and control of emerging zoonotic diseases.

The component includes:-

  • Disease surveillance system capable of early detection of emerging diseases.
  • A laboratory capable of providing recent and quick diagnostic test to assist in the early diagnosis and management of emerging disease.
  • Applied research capacity to assist in the identification of new pathogens and development of diagnostic tools.
  • Research into factors associated with the disease emergence including behavior factors.
  • Fastening links between human health and animal practitioner to ensure effective management of zoonoses.
  • Training programmes for epidemiologists, researchers, laboratory workers and clinicians.
  • Effective communication strategies at national and international levels.
  • Implementation of effective immunization schedule at national and international levels.
  • Implementation of strict quarantine rules for world animal trade and transportation as per the laid recommendation of WHO.




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