Science Page: African Swine Fever transmission and survivability

This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.

There is no Science Page this week so we are sharing a favorite from this year, in which Dr. Carles Vilalta created a literature review on ASF virus transmission and survivability.

Keypoints

  • New introductions of ASF to free areas of the disease are usually by uncooked pork fed to pigs.
  • Virus can be inactivated with temperature and low pH.
  • Survivor animals may play a role in the transmission and persistence of the disease.

Further outbreaks of African Swine Fever virus (ASFV) were reported last week in China several miles away from what is thought to be the first outbreak. This geographic dispersal leads us to think about dissemination mechanisms within the country and between countries.

EPIDEMIOLOGY

Infected animals will go through a viremic phase and can shed the virus through nasal secretions, feces and urine. Therefore, the main transmission route is oral-nasal, as pigs can be exposed to ASF positive secretions or tissues (i.e. pork products). Indirect transmission can also occur by exposure to contaminated fomites. This virus can also be transmitted by ticks. This vector-borne route becomes relevant when the wild boar
population is present and moves across regions and countries. The common introduction route into ASF free regions is usually through positive pigs transported into the area, or contaminated pork products that are fed to other pigs. ASFV has also been detected in air samples; however, airborne transmission is considered a secondary route of transmission due to the high virus load needed.

VIRUS SURVIVABILITY

Inactivation and persistence

Although ASFV is highly resistant, the virus can be inactivated at pH < 4 and pH >11. Survivability outside the host is heavily related to temperature. For instance, the infectious half-life in urine and feces can range from 3 to 15 days and 4 to 8 days at 37°C and 4°C, respectively. The virus may persist for several weeks or months in frozen, fresh, or uncooked pork, as well as in salted dried pork products. In contrast, ASFV is inactivated at high temperatures (i.e. 70°C cooked or canned hams) and in cured or processed products such as Spanish cured pork products after day 122–140 of curing. Pigs can become persistently infected and the virus can stay viable in their carcasses for up to six months. Therefore, infected carcasses represent a risk to other pigs. More recently, an investigation simulating a trans-Atlantic shipping of ASFV contaminated feed ingredients from Europe proved that viable virus can be recovered after 30 days.

The role of survivor pigs

ASFV recovered and sub-clinically infected pigs become a source of virus to other pigs. This plays an important role in disease transmission and persistence in endemic areas as well as becoming one of the most important routes of transmission into disease-free zones. In-vivo experiments have revealed an infectious period of moderately virulent virus isolates ranging from 20 to 40 days. In another in-vivo transmission study, pigs that had been exposed to ASFV 90 days prior were commingled with naive pigs and the virus was transmitted to naive pigs.

Serological field studies performed in positive regions of Brazil, the Iberian Peninsula, East Africa, Kenya and Uganda revealed that the there was a very low percentage of seropositive animals one year after the outbreak. It was hypothesized that those few seropositive pigs were still carriers and could have been responsible of some of the newer outbreaks.

CONCLUSION

ASF has a complex epidemiology with different routes of transmission that can involve animals and ticks as direct transmission, and contaminated clothes, tools, and surfaces as indirect transmission. Thus, early detection and intervention of the diseases are key to containing disease spread in absence of an effective vaccine.

Science Page: Protecting the Inevitable Risk; Biosecurity Evaluation at a Truck Wash

We hope you all had a great Thanksgiving! An ever increasing amount of you is visiting this blog every month so thank you, we appreciate your support!

This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.

This week we are sharing a report by Megan Bloemer on biosecurity at a truck wash. Megan, a 3rd-year veterinary student from the University of Illinois, presented this project at the Leman Conference this year and won the Morrison Swine Innovator Prize.

Key points:

  • Monitoring cab cleaning and hot shot handle cleaning via Glo Germ Gel is simple and cost-effective.
  • Wiping down the cab interior with intervention wipes only adds around 5 minutes. These minor cost and time additions to truck wash procedures can help to prevent a million-dollar PRRS break.
  • Truck wash crew and trailer washers are often overlooked but perform a job that is essential in maintaining biosecurity and disease outbreak and therefore herd health.

The objective of this study was to assess overall biosecurity at the truck wash and identify potential areas of concern, measure and evaluate these areas of concern, and suggest solutions.

Potential Areas of Concern Identified

Cab Cleaning

Glo Germ Gel under a UV light when the door handle was not cleaned (left) and was wiped down (right).

The areas observed for cleaning included: steering wheel, dash, handles, climate control buttons, and radio. These areas were not being focused on; but are critical areas touched each time a driver is in the cab. In addition, it was difficult for monitors to tell if a cab had been cleaned or not by visual inspection alone.

Equipment Movement

After the three-day observation period, it became apparent that all equipment besides hot shots stayed in the dryers. Thus, hot shots were identified as the main equipment of concern. They were not returning with each trailer load, leading to biosecurity concerns.

Monitor Movement

Monitors inspect both PRRS positive and PRRS negative trailers throughout the day, before the wash crew is allowed to disinfect each trailer. Although monitors change boots and put on Tyvek before inspecting negative trailers, there is no true clean / dirty line where they change shoes.

Evaluation

Cab Cleaning

Steering wheel, dash, door handle, climate control buttons, and radio control buttons were evaluated on how well they were cleaned with a Glo Germ Gel product. The Glo Germ Gel was applied while the trucks were waiting in line to be cleaned. The assessment was performed using an UV light for any trace of the Glo Germ, indicating whether the surface had or had not been cleaned. The interior of cabs were not being cleaned as well as possible as evidenced by the amount of fluorescence that was detected in those five critical areas.

Equipment Movement

All of the hot shot handles and prods were numbered in both the PRRS positive and PRRS negative equipment sheds on a Sunday. Every night for the next five days it was checked if each hot shot was present, which equipment shed it was in, and new ones were numbered as they appeared. Throughout the course of those five days hot shot handles and prods were not being returned on a consistent basis. However, the equipment was not switched between the PRRS positive and PRRS negative sheds.

Monitor Movement

Glo Germ Gel and Powder was applied to the shoes of monitors and on positive trailers before monitors inspected them. Although no Glo Germ was appreciated in the PRRS negative areas, it may still be a potential area of concern and should be further evaluated.

Interventions

Cab Cleaning

In order to ensure that the interior of cabs were being cleaned as well as possible,the truck wash crew was shown images of the cab interiors with the Glo Germ Gel comparing interiors that were wiped down and those that were not. Current protocols could be clarified, and the importance of cab cleaning should be emphasized. Glo Germ Gel also gives the monitors the ability to do random internal audits of cab cleaning.

Equipment Movement

In order to check hot shot handle and prod cleanliness Glo Germ can be applied at the same time monitors put Glo Germ in the cabs. To encourage returning hot shots the truck wash crew can continue to write down cull and gilt trailers that do not return with a hotshot. To stop any potential cross-contamination, the PRRS-positive hot shots could be painted red.

Monitor Movement

Although no Glo Germ was appreciated it is possible that monitor movement is still a potential biosecurity risk and should be further evaluated. It appears that the Glo Germ washed right off as the trailers were wet when the monitors inspected them.

Science Page: Emerging enrofloxacin and ceftiofur resistance in E. coli isolated from US swine clinical samples

This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.

This week we are sharing a report from Dr. Shivdeep Singh Hayer from the STEMMA lab, on the emerging enrofloxacin and ceftiofur resistance in E.coli in swine.

Key points:

  • Nearly one-third of clinical E. coli isolates collected from swine samples were ceftiofur or enrofloxacin resistant
  • Genetic analysis revealed presence of rarely reported genes in antimicrobial resistant isolates
  • Most of the isolates were multi-drug resistant on both routine lab tests and genetic analysis

In a previous study, we analyzed the antimicrobial resistance in Escherichia coli isolates recovered from swine clinical samples from across USA during 2006-2016 at the University of Minnesota Veterinary Diagnostic Laboratory (UMN-VDL), and found a 47% annual increase in the prevalence of enrofloxacin resistance (from 1.5% in 2006 to 32% in 2016) while no trend was observed for the resistance to ceftiofur (that ranged between 32-39%). A follow-up study was conducted to evaluate the genetic basis of resistance against enrofloxacin and ceftiofur in E. coli isolates using whole genome sequencing (WGS).

153 swine clinical E. coli isolates collected in 2014-15 from 14 states across USA were selected and genes causing ceftiofur and enrofloxacin resistance were identified using WGS.

21 (out of 106) enrofloxacin-resistant isolates from 6 states harbored diverse plasmid mediated quinolone resistance (PMQR) genes (qnrB19, qnrB2, qnrS1, qnrS2 and qnrS15). The presence of PMQR genes alone was associated with clinical levels of resistance.

The most prevalent genes associated with ceftiofur resistance were blaCMY-2 (89/106, 84%). Moreover, 24 ceftiofur-resistant isolates harbored various blaCTX-M and blaSHV genes.

Additionally,  bacteria carrying blaCTX-M and qnr genes also contained genes coding for resistance mechanisms against other antimicrobial classes and were commonly resistant against ampicillin, tetracyclines, gentamycin, trimethoprim and sulfonamides.

These genes (blaCTX-M, qnr) have been rarely reported from farm animals in USA and have been implicated as important genetic mechanisms behind extended spectrum cephalosporin and fluoroquinolone resistance in human and animal populations in several countries. These genes are present on plasmids, making their dissemination across bacterial populations faster by horizontal transfer.

The presence of multiple antimicrobial resistance genes on the same plasmids also makes mitigation of this problem more difficult because of the possibility that using one antimicrobial class will exert positive selection pressure for resistance against other antimicrobial classes.

Science Page: Illegal importation of meat derived food products through passenger airline carriers and possibility of disease introduction

This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.

This week we are sharing an article by the MSHMP team regarding the impact of illegal meat product importation on disease introduction.

Key Points:

  • Commercial airplane passengers bring illegal food imports
  • These illegally imported food products are an overlooked but important disease introduction source
  • The illegal importation by commercial travelers happens more frequently then generally assumed

Illegally imported products are a likely source of disease introduction

The recent African Swine Fever (ASF) outbreaks in China have created concern in the US swine industry over the possible introduction of the disease into the US, thus making Foreign Animal Disease (FAD) a primary topic of concern. One of the most pressing concerns about FADs in general, and ASF in particular, is what are the likely sources of entry, and how the associated risks can be mitigated. Illegally imported products, carried by commercial air passengers are often overlooked as a minor introduction source. Several studies around the world show that commercial air passengers do represent a likely source of disease introduction. Outbreaks of ASF, Classical Swine Fever (CSF) and Foot and Mouth Disease (FMD) have been attributed to feeding imported waste meat to domestic pigs (Falk, et al., 2013).

Thousands tons of illegal food products are found at airports

It is difficult to estimate the total amount of illegal food products entering a single country each year. A study conducted in Germany in 2015 at two major airports tracked seizures for three months, including an intensive 10 days of special controls where higher numbers of passenger luggage was searched. Based upon that data they estimated that each year 2,800 tons of illegal food products were brought in via the Frankfurt airport alone. The most commonly imported foods were meat and meat products, including raw, home cooked, preserved, and packaged foods (Beutlich, et al., 2015).

Another study, conducted in Switzerland estimated that the total volume of non-intercepted meat products were 8.6 tons for bush meat, and 1,013 tons for other meat products (Falk, et al., 2013).

Illegal food products contain pathogens; airports are risky ports of entry

A key point to understand the risk of improperly imported foods is knowing how often they contain pathogens and whether these have the capability of remaining infectious. In the German study, out of 474 samples tested, 5% of them contained food borne pathogens (Beutlich, et al., 2015). In a similar study conducted in Spain 67 out of 122 samples tested at an airport contained human noroviruses, and hepatitis E (Rodriguez-Lazaro, et al., 2015).

A modeling study focused on estimating the risk of introduction of ASF and CSF into the US using airport and customs data. The study identified specific airports (i.e.Washington-Dulles, George Bush-Houston, JFK-Queen, Warwick, Sanjuan, West Palm Beach, Charlotte, Ft. Lauderdale, Newark and Cleveland) as ports of entry with the highest risk for both ASF and CSF introduction. This work also identified the months of May through July as the months with the highest risk (Jurado, Paternoster, Martínez-López, Burton, & Mur, 2018).

Only a fraction of illegal imports are intercepted

It is estimated that only between 10-50% of improperly imported products are intercepted at customs (Jurado, Paternoster, Martínez-López, Burton, & Mur, 2018).One study’s sensitivity analysis showed that for both ASF and CSF, the likelihood of detecting illegal products was highly correlated with the final risk of disease introduction.This means that an increase in customs detection of products brought by commercial passengers largely reduces the risk of a CSV or ASF introduction into the US (Jurado, Paternoster, Martínez-López, Burton, & Mur, 2018).

Pork products were seized recently in the USA and Japan

Recently, on October 15th, 2018 a customs and border protection beagle found a whole roasted pig in the luggage of a traveler from Ecuador(Lieu, 2018) at the Hartsfield-Jackson Atlanta airport. Ecuador as any other South American country is ASF negative, but CSF continues to be present in the country. It is unknown whether the smoked pig has been tested for CSF, but the case is a perfect example of the variety of products that are being transported to the US.

On October 1st, Japanese customs officials confiscated a pork sausage from a Beijing traveler. The sausage tested positive for ASF (Reuters). African Swine Fever has also been found at a South Korean airport in pork products brought in a commercial passenger airline from China (Reuters). All of these examples highlight the reality of the risk illegally imported products carried by commercial travelers play in FAD introduction.

It is important for the swine community to be aware of these risks, to be aware of what food products are being brought to their sites by people, and to push for effective prevention methods. It also highlights the need of the swine community to communicate this risk to the non-swine community to raise awareness and thus contribute to protecting the industry. By using research that helps identify where the highest risks lie spatially and temporally, as well as flights from which countries represent risk, better prevention methods can be developed and implemented.

The effect of season on PRRS time-to-stability in the Midwestern United States

This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.

Key Points

  • Seasonal conditions may effect the time to stability of a farm
  • Understanding seasonal effects on time to stability can help producers and veterinarians plan herd closures

This week, we are sharing a report by the MSHMP team in collaboration with Dr. Andreia Arruda from the Ohio State University regarding the impact of seasons on PRRS time-to-stability.

The time needed between an outbreak and consistently weaning porcine reproductive and respiratory (PRRS) virus PCR negative pigs is referred to as time-to-stability (TTS). In this analysis we describe differences in TTS according to the season when the PRRS outbreak occurred in farms located in the Midwestern United States.

161 PRRS outbreaks in 82 sow farms were classified based on the date of the outbreak:

  • March 21st to June 20th: Spring
  • June 21st to September 20th: Summer
  • September 21st to December 20th: Autumn
  • December 21st to March 20th: Winter

TTS was calculated as the time from the reported PRRS outbreak to the time of the last PRRS PCR negative result in wean-age pigs.

A significant difference was detected in TTS among seasons. The median TTS was higher in spring and summer, compared to autumn and winter.

An explanation for the observed TTS difference among seasons may be found in environmental survivability of the virus as for PRRS outbreaks that occur during spring or summer, the last phase of the stability process coincides with the arrival of winter where the reduced ventilation and decreased temperature within the farm may favor PRRS survival resulting on a lower likelihood of elimination during this time.

PRRS time to stability season

Science Page: Making epidemiological sense out of large datasets of PRRS sequences

This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.

This week, we are sharing an epidemiological report regarding a large PRRS sequence dataset from Dr. Igor Paploski in the VanderWaal research group.

Key points:

  • Occurrence of PRRS lineages is not equal in different years, systems or production types
  • Occurrence of specific PRRS lineages is associated with movement of animals
  • Continuous surveillance for PRRS occurrence is important in understanding its determinants and might be able to provide insights that can
    help on its prevention

By utilizing a dataset of 1901 PRRS sequences provided by the Morrison Swine Health Monitoring Project (MSHMP) participants over 3 recent years, the spatiotemporal patterns in the occurrence of different lineages of PRRSV was described and the extent to which the network of pig movement between farms determines the occurrence of PRRS from similar lineages was investigated.

PRRS lineages occurred at different frequencies across geographically overlapping production systems. Preliminary analysis showed that the relative frequency in which specific lineages occur increase while others are decrease over time. The rate at which these changes occur appears to be system-specific. Some lineages were also more common in farms of specific production types (i.e. sow farm or nurseries). As expected, farms that were connected via pig movements were more likely to share the same lineages than expected by chance across all years.

These findings suggest that system-specific characteristics partially drive PRRS occurrence over time and across farms of different production types. Our results also
indicate that animal movement between farms is a driver of PRRS occurrence, strengthening this hypothesis of viral transmission.

Additional research is needed to quantify risks and develop mitigation measures related to animal movement.

Large PRRS sequencing dataset

Science Page: Quarterly review of MSHMP reported PRRSv Restriction Fragment Length Polymorphism (RFLP) patterns

This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.

This week, we are sharing a report from the MSHMP team regarding reported PRRS RFLP patterns.

Keypoints:

  •  Recording PRRSv RFLP and sequences will provide better insights into the epidemiology of the disease at local, state and national level.
  • Building a RFLP database will allow us to assess which factors could be involved or related with the emergence of a new RFLP.
  • The predominant pattern RFLP in this quarterly review is the 1-7-4.

In the first quarter of the 2018/2019 incidence year, 20 breaks affecting 12 production systems were reported. Out of these, 4 occurred in July, 13 in August and 3 in September.

Of those 20 farms, three had a break while still being status 1, one was status 2 in the process of eliminating the disease (not using any immunization protocol at that point), 6 were using field virus as the acclimatization protocol (2fvi), 8 were using vaccine (2vx), one was provisionally negative (status 3) and one broke from a status 4 after being almost 4 years completely negative (see figure below).

RFLP patterns with status at break

The distribution of the breaks is wide and affects different states. Thus, we had 6, 1, 4, 1, 4, 2, 1 and 1 break in the states of IA, IN, MN, MO, NC, NE, OK and PA, respectively. The closest 2 farms that broke were 1.2 miles apart, belonged to the same company and had the break a week from each other (no sequences was provided).

Eight out of the 20 breaks reported were accompanied by the associated RFLP. The predominant (4 out of 8) RFLP pattern since July is 1-7-4. Iowa was the state with the highest number of 1-7-4 cases.