Highlights report cattle-October 2024

Polluted grassland after a distribution centre fire

Early in May 2024, several reports were received on the Veekijker hotline about polluted grassland after a fire at a distribution centre in Oss. The fire spread items such as the remains of solar panels around the surrounding area. Two livestock farmers and their veterinarian were worried about the contamination that they came across on their land and wondered whether the grass was safe for cows to graze.

Following on from these reports, a Veekijker veterinarian visited the affected farms. The land was inspected and various materials collected and taken away for further tests. The material was largely insulation, melted and charred pieces of plastic that contained metals, and thin vitreous material (residues from solar panels). In consultation with GD’s toxicologist, a decision was taken – both on animal health grounds and because of the potential risks to public health – to examine the materials collected for the presence of heavy metals. Additionally, GD’s pathology department was consulted to get an estimate of the possible consequences of ingestion of these materials along with the feed. A practice expert was also contacted who had spoken to the Veekijker hotline last year about a similar fire and contaminated grassland, to ask about their experiences with animal health at the cattle farms affected at the time. The pathologist assessed the risk of animal health problems after feed intake as being low. The person with experience of the previous cases stated that there had been no more cases observed at the affected farms of Hardware Disease or intestinal obstructions. No concentrations of heavy metals (including lead and calcium) that could give cause for concern were found in any of the samples tested. The highest metal concentration observed was for zinc in the charred materials (at 3 to 30 grams per kilogram). Zinc levels do not rapidly become toxic for cattle, but can be toxic at more than 5 milligrams per kilogram of feed that is ingested for a lengthy period. Calves are somewhat more susceptible to toxicity. High zinc levels disrupt the calcium metabolism and can thereby increase the risk of hypocalcaemia. If an elevated zinc concentration is present for a lengthier interval, it can also reduce the uptake of copper and thereby raise the risk of copper deficiency developing. Although it is advisable to remain alert, it is unusual for zinc levels to be the principal cause of either of these conditions. Based on the toxicological analysis, GD’s pathology department’s assessment and experience from practice, the risk of letting cattle graze the grass seems acceptable. It is recommended that as much of the industrial material as possible should be removed from the grassland and that you should stay alert for signs of health problems such as sharp objects affecting the rumen or symptoms of elevated zinc intake.

Figure 1: Photos of material found in surrounding grassland after a fire in a distribution centre.

Confusion over diagnosing Lactococcus spp. as the cause of mastitis

In the second quarter of 2024, veterinary practices regularly approached the Veekijker and the Udder Health team (UGA), stating Lactococcus spp. as the diagnosis for mastitis more frequently than in the past. This signal is not backed up by studies at GD into the causative agents of mastitis: once again this quarter, Lactococcus spp. represents less than 1 per cent of the causative agents for mastitis. Lactococcus spp. are Gram-positive cocci that – along with Enterococcus spp. and Aerococcus spp. – are classified in the group ‘other streptococci’ (environmental streptococci and streptococcus-like

bacteria). Lactococcus spp. are difficult to distinguish from Streptococcus uberis using classical detection methods (such as biochemical testing). Veterinary practices stated that they had diagnosed Lactococcus spp. as the cause of mastitis and differentiated it from Streptococcus uberis on the basis of an antibiogram carried out at the practice. Streptococcus spp. are intrinsically resistant to aminoglycosides such as e.g. neomycin and kanamycin. Streptococcus spp. typically have small inhibition zone diameters in an antibiogram based on agar diffusion with paper discs (as

widely used in practice). Lactococcus spp. mostly have larger inhibition zone diameters for aminoglycosides than Streptococcus species. This identification is however not conclusive because the values of the inhibition zones of Lactococcus spp. can overlap with those of Streptococcus spp. Only molecular tests such as PCR, whole-genome sequence analysis and MALDI-TOF MS are suitable for definitive identification.

Severe effects of suspected poisoning with ragwort and/or aflatoxins

At the end of the first quarter, a veterinarian approached the Veekijker with a case that continued through to the second quarter. Several heifers at a cattle farm died during a short period some six months ago at the farm’s young cattle site. The hypothesis at the time was that common ragwort may have been present in the hay that was fed to them. Subsequently, several older heifers at various lactation stages died at the dairy cattle site. These heifers were from the same group as the ones that had become ill or died at the earlier stage. The sick animals’ production levels and cud-chewing went down over several days, after which they finally died. Despite the absence of specific disease symptoms, their appetites were greatly reduced and they only wanted to eat hay. Shortly before they died, all the older heifers exhibited the same clinical picture of a central nervous system disorder as the younger ones that had died: lying down, groaning, stamping their feet, symptoms of shock and several cases of rectal prolapse. Similar issues were not observed among the other dairy cows and the other young cattle. At the moment the problems appeared, they were being fed lower-quality green silage in which a few mould spots were visible. Because of suspicions that this silage was playing a role in the issues, the practice

expert advised the livestock farmer to remove the silage and replace it with better-quality silage. One heifer was also submitted for necropsy. The Veekijker veterinarian also advised carrying out blood tests on a few sick heifers from both age groups, for general screening (hepatic values) and investigation of vitamin and mineral levels. This was followed by advice to test the silage for mycotoxins and to have a necropsy carried out if another animal died.

A total of two animals were submitted for pathological examination. Both had a firm liver with extensive fibrosis. This clinical picture is seen in chronic intoxication with pyrrolizidine alkaloids (PA), such as those present in ragwort, and/or intoxication with aflatoxins. Distinguishing between these causes was not possible based on the histological picture. A high copper level was also found in the first animal. Hepatic encephalopathy was observed in the brain, explaining the clinical picture of a central nervous system disorder shortly before death. The GD toxicologist stated that detecting aflatoxins in the animal’s tissues is not something that can be routinely tested. The presence of both aflatoxins and common ragwort in the feed can be demonstrated. It was unfortunately no longer possible to test for mycotoxins or ragwort in the silage that

was fed, given that the livestock farmer had removed the silage on advice from his veterinarian. Given the problems with the younger heifers last year and the older ones from the same group this quarter, it is suspected that this batch of animals had already suffered liver damage (from PA in the hay fed to them) and that they are now more susceptible, as older heifers, to mycotoxins, high copper concentrations in the feed or re-exposure to PA. Given that this hypothesis could mean that the remaining animals from the same batch might also have liver damage, the Veekijker veterinarian recommended testing more animals through a blood test of the hepatic parameters. Various animals did indeed have abnormal liver values to a greater or lesser extent. In the end, the livestock farmer lost 75 per cent of the animals from this group. There were further deaths in the months after the initial contact with the Veekijker as well. The livers of some dead animals were submitted; these showed a picture of severe chronic liver damage with extensive fibrosis, possibly caused by aflatoxins or pyrrozolidine alkaloids. The insurance company was brought in to reimburse the animals lost.

Streptococcus agalactiae mastitis outbreaks with a varying picture

The udder health team (UGA) was approached through the Veekijker hotline after several diagnoses of mastitis caused by Streptococcus agalactiae (SAG). In the first case, the veterinarian of a dairy farm that routinely has its bulk milk tested for mastitis contacted the Veekijker because SAG had been detected in the bulk milk for the first time. There were no problems at the farm at that moment. Shortly afterwards, however, several cows developed clinical mastitis (grade two) for which SAG was detected in the affected quarters by bacteriological examination at the veterinary practice. The bulk somatic cell count also increased. It was decided to trace the SAG carrier cows and keep the milk from these animals out of the tank. The SAG mastitis cases proved difficult to treat and many of the infected quarters ultimately went dry. During a farm visit by a zootechnical specialist in udder health from GD, it was determined that none of the typical risk factors applied (such as recent cattle purchases or a fall in resistance). The case was followed up further as part of a GD project and the SAG isolates that had been retained were sent to GD. A cluster analysis was able to show that the six isolates analysed from five cows were related (a single

cluster). The isolate from the bulk milk was also shown to be related. This cluster analysis result indicates that the SAG outbreak at this farm probably had a single source of infection. A striking feature at this farm was the large number of cows with clinical mastitis; this does not happen very often with SAG. Another farm contacted the UGA team because of a very high bulk somatic cell count. This farm also participated in the Mastitis Bulk Somatic Cell Count study and gave positive test results for SAG and Staphylococcus aureus in two years, with a varying bulk somatic cell count. Following on from that phone contact, GD carried out bacteriological examinations of the milk from all the udder quarters of fifteen cows. SAG was detected in eleven cows (27 quarters). A veterinarian from the udder health team visited the farm and once again, the typical risk factors were not seen. Suboptimal functioning of the milking machine may have played a role in the occurrence of the problems. Additional milk samples were taken for bacteriological testing and SAG was detected in five more quarters (from three other cows). Almost all the quarters that were examined had a high cell count. This shows the importance of also sampling quarters with

a low cell count so that no SAG infections are missed. Isolates from this farm were also retained, with ten of them included in the cluster analysis. These isolates were shown to belong to four different clusters. What stands out at this farm is that the bulk milk had already been positive for SAG for two years before the bulk somatic cell count increased dramatically. Unlike the situation at the first farm, not many cases of clinical mastitis caused by this bacterium were observed here. The livestock farmers and practice experts at the two farms have tackled the SAG problems and followed them up; SAG was no longer detected in the most recent bulk tank milk samples. Although the annual numbers are still low, SAG seems to be becoming more prevalent (in bulk milk) in both Flanders and the Netherlands (source: MCC Vlaanderen). The bacteria seem to exhibit variable behaviour. The classical picture of subclinical mastitis – rapid spread and an increasing bulk somatic cell count, with a good response to therapy – seems to be changing. This should be investigated further to improve what we know about SAG and to optimise how it can be tackled on farms.

Veterinary practice networking visits and monitoring meetings

Most of the networking visits to veterinary practices this year were carried out in the second quarter. The Veekijker veterinarians visited veterinary practices from the network to inform them about the findings from the monitoring programmes and to gather information from the working domains of the practices. These visits provide not only an

additional route for picking up signals from the field but also more personal contact between the Veekijker veterinarians and the veterinary practices.

There will once again be monitoring meetings for cattle veterinarians at various locations throughout the country in November and

December 2024. Practitioners from all the veterinary practices will be invited for these. Various topics arising from the monitoring will be discussed, along with a few more in-depth studies.

Health of cattle in the Netherlands, second quarter of 2024

VETERINARY DISEASES

Implementing Regulation (EU) 2018/1882 of Animal Health Regulation (AHR) 2016/429 (category A disease)

Lumpy Skin Disease (LSD) Viral infection. The Netherlands is officially disease-free.

Foot and Mouth Disease (FMD) Viral infection. The Netherlands has been officially disease-free since 2001.

A, D, E No infections ever detected.

A, D, E No infections detected.

Implementing Regulation (EU) 2018/1882 of Animal Health Regulation (AHR) 2016/429 (categories B to E)

Bluetongue (BT)

Bovine genital campylobacteriosis

Bluetongue serotype 3 (BTV-3) outbreak in the Netherlands since September 2023.

Bacterium.

The Netherlands has been disease-free since 2009. Monitoring of AI and embryo stations and of animals for export.

Bovine Viral Diarrhoea (BVD) Viral infection.

Control measures compulsory for dairy farms but voluntary on beef cattle farms.

C, D, E Three infections notified. Vaccines are available in the Netherlands. About 23 per cent of dairy cows have antibodies to BTV-3 after the 2023 outbreak.

D, E Campylobacter fetus spp. Veneralis not detected.

C, D, E

Brucellosis (zoonosis, infection through animal contact or inadequately prepared food)

Bacterium.

The Netherlands has been officially diseasefree since 1999. Monitoring via antibody testing of blood samples from aborting cows.

Enzootic bovine leukosis Viral infection.

The Netherlands has been officially diseasefree since 1999. Monitoring via antibody testing of bulk milk and blood samples from slaughtered cattle.

Epizootic Haemorrhagic Disease (EHD) Viral infection.

Detected since 2022 in cattle in Europe (Spain, Italy, Portugal and France)

Infectious Bovine Rhinotracheitis (IBR) Viral infection.

Control measures compulsory for dairy farms but voluntary on beef cattle farms.

The status of 90.9 per cent of the participating dairy farms is favourable (BVD-free or BVD not suspected)*

The status of 20.1 per cent of all non-dairy farms is favourable (BVD-free or BVD not suspected).

* The BVD status as determined according to the GD programme.

B, D, E No infections detected.

C, D, E No infections detected.

Anthrax (zoonosis, infection through contact with animals)

Bacterium. Not detected in the Netherlands since 1994. Monitoring through blood smears from fallen stock.

D, E No infections detected.

C, D, E

The status of 82.4 per cent of the participating dairy farms is favourable (IBR-free or IBR not suspected).

The status of 20.9 per cent of all non-dairy farms is favourable (IBR-free or IBR not suspected).

D, E No infections detected.

VETERINARY

Implementing Regulation (EU) 2018/1882 of Animal Health Regulation (AHR) 2016/429 (categories B to E)

Paratuberculosis

Bacterium.

In the Netherlands, the control programme is compulsory for dairy farms. 99 per cent take part.

Rabies

(zoonosis, infection through bites or scratches)

Bovine tuberculosis (TB) (zoonosis, infection through animal contact or inadequately prepared food)

Trichomonas

Q fever (zoonosis, infection through dust or inadequately prepared food)

Viral infection.

The Netherlands has been officially diseasefree since 2012 (an illegally imported dog).

Bacterium.

The Netherlands has been officially diseasefree since 1999. Monitoring of slaughtered cattle.

Bacterium.

The Netherlands has been disease-free since 2009. Monitoring of AI and embryo stations and of animals for export.

Bacterium.

In the Netherlands, this is a different strain to the one on goat farms and a relationship with cases of disease in humans has not been established.

From the first quarter of 2023 onwards, this is once again part of the standard necropsy protocol for aborted foetuses.

E The status of 82.5 per cent of dairy farms is A (‘not suspected’) in the PPN (Paratuberculosis Programme Netherlands) or 6 in the IPP (Intensive Paratuberculosis Programme).

B, D, E No infections detected.

B, D, E No infections detected.

C, D, E Tritrichomonas foetus not detected.

E Three infections detected in aborted foetuses.

Article 3a.1 Notification of zoonoses and disease symptoms, ‘Rules for Animal Husbandry’ from the Dutch Animals Act

Leptospirosis

(zoonosis, infection through animal contact or inadequately prepared food)

Bacterium.

Control measures compulsory for dairy farms but voluntary on beef cattle farms.

Listeriosis

(zoonosis, infection through inadequately prepared food)

Salmonellosis

(zoonosis, infection through animal contact or inadequately prepared food)

Yersiniosis

(zoonosis, infection through animal contact or inadequately prepared food)

Bacterium.

Infections have occasionally been detected in cattle.

Bacterium.

Control measures compulsory for dairy farms but voluntary on beef cattle farms.

Bacterium.

Infections detected occasionally in cattle, mostly in aborted foetuses.

- The status of 98.3 per cent of dairy farms is ‘leptospirosis-free’.

The status of 30.0 per cent of all non-dairy farms is ‘leptospirosis-free’.

Animals are still arriving with a leptospirosis status poorer than ‘free’ but the numbers are less than in the previous quarter.

Two dairy farms reported with new leptospirosis infections.

- Infections detected in five cattle and four aborted foetuses presented for necropsy.

- The bulk milk results of 98.5 per cent of dairy farms are favourable (first round of a nationwide programme).

- No infections detected.

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VETERINARY DISEASES SITUATION IN THE NETHERLANDS

Regulation (EC) no. 999/2001

Bovine Spongiform Encephalopathy (BSE)

Prion infection.

The OIE status for the Netherlands is ‘negligible risk’. Monitoring has not revealed any further cases since 2010 (total from 1997 to 2009: 88 cases).

Other infectious diseases in cattle

Malignant Catarrhal Fever (MCF)

Viral infection.

There are occasional cases in the Netherlands of infection with type 2 Bovine herpes virus.

Liver fluke Parasite.

Liver flukes are endemic in the Netherlands, particularly in wetland areas.

Neosporosis Parasite.

In the Netherlands, this is an important infectious cause of abortion in cows.

Category (AHR)

Table continuation

Surveillance – Highlights Third Quarter 2023

- No infections detected.

Tick-borne diseases

External parasite that can transmit infections.

Ticks infected with Babesia divergens, Anaplasma phagocytophilum and Mycoplasma wenyonii can be found in the Netherlands.

- Two infections confirmed upon necropsy.

- Infections were detected at five farms and in two cows presented for necropsy.

- Infections were detected in two aborted foetuses presented for necropsy.

- No samples submitted for examination.

Animal health monitoring

Since 2002, Royal GD has been responsible for animal health monitoring in the Netherlands, in close collaboration with the veterinary sectors, the business community, the Ministry of Agriculture, Nature and Food Quality, vets and farmers. The information used for the surveillance programme is gathered in various ways, whereby the initiative comes in part from vets and farmers, and partly from Royal GD. This information is fully interpreted to achieve the objectives of the surveillance programme – the rapid identification of health problems on the one hand and the following of more general trends and developments on the other. Together, we team up for animal health, in the interests of animals, their owners and society at large.