Reported outbreaks of goat pox worldwide yields differing mortality rates with 7% in Sudan , 21% in Iraq  and 30% in India . In this study, a much lower mortality rate was found despite a rather high morbidity rate high probably as a result of the study population containing comparatively fewer of the 3-6 months old goats. It has been shown that maternal antibody for goat pox is maintained for about 3 months and those animals older than 6 months that survived an infection will have life-long immunity [8-9]. This phenomenon explains the susceptibility of those in the 3-6 months old  which should yield higher morbidity rate. However, since the number of animals under this group is quite low, the mortality rate has failed to surpass those of other groups.
The number of dead animals during the outbreak depends on the virus virulence, size of the population and their susceptibility and on the basic reproductive number i.e, average expected number of secondary cases produced by a single infection in a completely susceptible population . However, these rates may vary depending on additional factors including breed  and the most notably the herd immune status . Recently published data showed that case fatality rate of goatpox disease ranged from 21.4 % to 60 % [13-15]. Likewise, the high fatality rate in the present study underlined the need for a much more effective control of goat pox along with the requirement to vaccinate susceptible herd or in endemic areas. However, the difficulty in implementing such health programs in Vietnam is explained below.
A 23% morbidity rate based on seroprevalence has been documented in nomadic goat herds in Punjab . It is not suprising to see a higher infection rate in the extensive system as previously reported . However, this rearing method is popular with poor farmers in lowland and mountainous areas in Vietnam who could not afford to spend on a standard health management. Goats under the extensive system forage freely in a wide area exposing them increase chances to be exposed to the virus. These goats might have also been exposed to lesser domestication, maintaining many of the behavioural traits of the wild types such as aggressiveness [17-18]. Furthermore, goats especially under the extensive system being naturally aggressive  predisposes the body to injuries making easier access of the virus when inoculated. This is an added problem since most of the goats were not dehorned (due to financial constraints) making injuries prone to infection during a fight. On the contrary, the low infection rate under the intensive system could have resulted from a much more efficient disease control program that has minimized spread of the virus within the herd. However, the benefits of extensive farming system can be still exploited by taking advantage of its eco-agrarian nature. It can economically ultilise marginal or unused land that can be later be easily adapted by the goats. Such conditions had less stressful effect on the goats making them much more hardy to harsh conditions. This is an opportunity for the poor rural farmers with limited financial resources and knowledge in commercial goat farming. This can be improved if there is provision of extension veterinary officers to offer guide and assistance in goat farming.
Undoubtedly, defining the vulnerable period of infection is one of the most important measurement to be known for an effective disease management . In the study presented here, the most susceptible age were goats of 3-6 months old which conforms to findings of  and  who found that the chance of infection chance in the young was 2.2 times greater than that of an adult. However, contradictory results were seen if infection rate was based on seroprevalence. Fentie et al.  demonstrated a low infection rate in older animals although this appeared to refute earlier published findings . Nevertheless, in the latter study , age groups were not clearly defined which may have led to a less homogenous groupings. Additionally, the collected samples from slaughter house, tanneries and hide markets where probable that few samples were collected from goat kids to be devoid . The age grouping the study presented here was based on the main purpose of meat goat breeding in Vietnam. The indigenous and mixed breed of Vietnamese goat attained a market weight of 25 to 30 kilograms at 6 months old age, justifying a 3 month interval being chosen.
Recognising the key salient clinical signs is key factor for field diagnosis of goat pox . The prominent clinical signs seen in this study too were depression and being much more severe in kids [22-23] accounting for systemic signs of pyrexia. About 85.01% of affected animals showed varying degrees of anorexia associated with the development of lesions on mucus membrane of the face. The lesion commences as red patches around the mouth, nose and eyes which later swelling into a papule. These papules trigger lacrimal, nasal and saliva discharges. Respiratory distress and secondary bacterial pneumonia are predominant in kids which could not survival malignant stage [6, 24-25]. In adult goats, the ulceration of papules renders difficulty for digestive and breathing activities which in turn worsen productive performance. The goats with conjunctivitis, corneal opacity and blepharitis emulated the acute phase pox disease . The development of pox lesions is observed over the animal body especially hairless areas (face, pinna of the ears, udder, genital, anus, under the tail). The red patches turn to hard rubbery papules and become vesicles after 3 to 4 days. Necrotic papules formed pustular as the result of thrombosis and localised ischaemia. Dark hard scabs are formed by the remnant of necrotic papules [6; 25-27].
Although the overt clinical signs of goat pox are quite characteristic, the less severe manifestation needs to be judiciously distinguished from several other closely resembling diseases. The closest would be contagious ecthyma (orf) which affects young kids while goat pox involves all ages. The signs are usually that of flat or dome-shaped bullae crust around the commissures of mouth which left no scar after healing  as opposed to a rather permanent papular lesion in goat pox. Blue-tongue may be confused with goats pox although the goats are less less susceptible with signs rarely seen in goat pox i.e localized oedema, haemorrhages and erosion of mucous membrane. The post mortem lesions of blue tongue are that of effusion in the thoracic cavity and pericardial sac . High mortality is seen in peste des petits ruminants (PPR) which affects mainly young goats that showed signs of coughing; halitosis, erosive oral lesion and severe diarrhoea. These signs are not seen in goat pox along with rather pathognomonic lesion of PPR comprising of zebra stripes of gastro-intestinal tract and pneumonia . Lastly, a likely differential to be considered to goat pox is dermatophilosis  where the latter exhibited signs of paintbrush matted hair all over the body that is not a feature of goat pox.
In this study, for all PCR positive cases, the clinical and post mortem lesions were 100% present in the skin and lungs of affected goats. It is likely that owing to the epitheliotropic nature of the virus lesions were predominantly seen in the skin, lung and discrete sites within mucosal surfaces of oro-nasal and gastrointestinal tissues . As evidenced in this study and as reported earlier in similar studies, the role of skin and lung as a target organ  for the virus leads to much more deposition of the lesion in these tissues [33-34]. Beside darkened circumscribed pox lesions [33, 35], the entire lung are pale pink with loss of sponginess. Congested trachea contain blood or fluid-filled vesicles with involvement of the lymph nodes. As seen in the study presented here, calcified nodules are found the most abudant in large intestine (rectum) of goats that were mildly affected [21,36].
Histopathological findings in the study presented here were in accord to previous publications registering marked change in the epidermis. The degeneration of epithelial cells, hyperkeratosis, ballooning and degeneration of proliferating epithelial cells along with inflammation led to the desquamation of skin layers. Variable observation of lung microscopy include haemorrhage, congestion and thickening alveoli wall which resulted in narrowed alveoli. Secondary bacterial infection has invoked infiltration of inflammatory cells to affected regions of the lung [6, 37-38].
The PCR-based test is chosen because of its sensitivity and simplicity . The sensitive and simple PCR assay has confirmed caprine pox virus in the biopsy samples . Almost 80% of the samples were positive with amplicon size of 172 bp although no attempt was made to identify and differentiate of caprine pox virus [1, 22, 41-42]. However, the isolates from this study did not show much variation compared to those reported in China . This could be explained by the fact that although phylogenetically China has three main subgroups of goatpox, only one is circulating in the south i.e bordering Vietnam .
These findings pose a challenge to the aspiration of Vietnam’s to transform the future potential of goat farming into an industry. The local consumer prefers fresh chevon than frozen products due to food safety issues linked to the weakness of their cold chain system . Furthermore, goats as well as being a form of meat for the family and community, goat serves as a cash reserve for the poor farmer .
The current study also revealed most of the goat husbandry system is mainly extensive which may hamper the possibility to initiate goat production within the mountainous areas. Likewise, as revealed here, goats reared under the intensive system offers a better farming milieu for disease control which the farmer or nation should adopt to improve productivity. Under an intensive system, the ease to isolate and locate an infected animal and area enabling an effective diagnosis and thus control and prevention. It is rather difficult or almost impossible to perform such tasks (isolate and locate) under free grazing or nomadic conditions. Nevertheless, Vietnam should make formidable reforms to the livestock industry since goats in Vietnam are still (as found in this study) and in future will be reared by the poorer farmers halting an increase in goat population and productivity. This is even much more worrying especially with respect to a lack of herd health program (disease control). Thus, in order to bring the industry to greater heights, offsetting devastating disease like goat pox is mandatory. It is believed that these findings on goat pox will facilitate the government to continue working on improving disease identification and control to avoid hindrance in goat production.