to finish
In the fourth quarter of 2024, in response to reports received through the Veekijker and from pathology, two interesting pilots were launched and completed. These give a nice understanding of how animal health monitoring works in the Netherlands and what is done ‘behind the scenes’ with the incoming notifications.
We discuss two cases from start to finish: from the initial report received through the Veekijker hotline or from the necropsy lab to the outcome of the pilot study. The first case study started when the Veekijker veterinarians received a striking number of calls from vets in the field in September and October, asking about eye abnormalities in calves. The second case study began in the pathology lab when several breeding calves were diagnosed at the end of the third quarter and in the fourth quarter of 2024 with the unusual diagnosis of fibrinous polyserositis caused by Mannheimia haemolytica (Mh); this condition is generally seen in veal calves.
Eye disorders pilot Trigger
In September and October, large numbers of reports about eye abnormalities in calves were received by the Veekijker over the course of just a few weeks. We would normally receive an average of two to four calls about this, but in September and October there were ten and sixteen respectively. The vets were describing calves with a blue-white haze over the eyes, in some cases combined with a tapering protrusion, distorting the eyeball. In later stages, the eyes of in some calves had ulcers (some perforated), secondary infections and deep blood vessel formation. The calves had little or no vision. The reports were about calves in the 0-14-day age category on dairy farms, as well as calves older than 14 days on veal calf farms. Eye abnormalities can be caused by Moraxella bovis (pinkeye), Mycoplasma bovis, septicaemia, congenital hypovitaminosis A, malignant catarrhal fever (MCF) and congenital bovine viral diarrhoea (BVD) infection. It was also described in calves during the bluetongue virus (BTV) serotype 8 outbreak in the Netherlands in 2007. In some affected calves, previous investigations had shown both BTV antibodies and virus. It was unclear whether the individual mothers of affected calves had also experienced bluetongue infections and/or had been vaccinated. Given the age of the youngest calves, the possibility of antibodies being transferred through the colostrum was taken into account. After discussions in the Veekijker team, it was decided to launch a pilot study to enable these signals to be interpreted better.
Follow-up
A pilot proposal was written and then reviewed by the Animal Welfare Authority, given the involvement of live animals in the clinical diagnostics being performed. The pilot study that was drawn up aimed to answer questions about the onset, clinical picture, evolution and recovery of the condition, as well as the possible association with BTV-3. A dairy farm, a youngstock rearing farm and a veal calf farm were visited. On these farms, the case histories were taken and several calves with eye abnormalities were examined clinically, including a comprehensive eye examination. Photographic and video material was collected during the examinations for later review if necessary. In addition, samples were taken from the calves and (where possible) their mothers. Blood samples from ten calves were tested for BTV (by PCR), BTV antibodies (by ELISA), BVD virus (by PCR) and BVD antibodies (by ELISA). Eye swabs from the calves were examined bacteriologically (for both aerobic and anaerobic bacteria). Blood samples from the mother animals (where available) were tested for BTV virus and BTV antibodies.
Outcome
The calves in this pilot were not born with eye defects but developed them over a period ranging from two days up to several weeks of age. Eye examinations showed that nine out of the ten calves exhibited corneal oedema, in some cases associated with ulceration of the cornea, keratoconus and varying degrees of blindness (see Figure 2). No other unusual clinical symptoms were observed. The severity of the corneal oedema varied, as did the time to recovery, with the oedema sometimes disappearing completely without permanent damage, according to the farmers concerned. Both BTV virus particles and BTV antibodies were detected in all the calves with corneal oedema. BTV virus and BTV antibodies were also detected in the mother animals that were examined. The BVD virus was additionally detected in one calf and another had antibodies to BVD as well as to BTV. Eye swabs showed no evidence of Mycoplasma bovis; Moraxella bovoculi was cultured in a single case. The findings, for which the presence of BTV virus and BTV antibodies was the only common factor, suggest an association between BTV infection and the observed ocular abnormalities (specifically corneal oedema) in the calves studied.
Figure 2: Photographs of the eyes of two calves examined as part of the pilot study, clearly showing corneal oedema and keratoconus.
Trigger
At the end of the third quarter and during the fourth quarter of 2024, it was striking that several cases of polyserositis caused by Mannheimia haemolytica (Mh) were diagnosed in breeding calves on pathological examination. Polyserositis is a condition in calves aged from about three weeks to several months. It is an acute or peracute infection of the peritoneum, pleura and/or pericardium, in which calves that were in good condition are suddenly found seriously ill or dead. Over the past fifteen years, the percentage of veal calves with polyserositis caused by Mh has increased. Studies have shown that this is due to Mh serotype A2, whereas Mh serotype A1/A6 is often diagnosed in pleuropneumonia in dairy cattle. Although polyserositis is a wellknown clinical picture in veal calves, it is rarely seen in breeding calves. To gain a clearer picture of what these section findings mean, it was decided to launch a pilot study.
Follow-up
This pilot study investigated how frequently polyserositis caused by Mh has been diagnosed in breeding calves over the past 22 years, and a farm visit was also conducted. Samples were taken at the farm where one of the calves originated. These samples were examined by PCR, bacteriological tests, susceptibility testing and whole genome sequencing (WGS). The veterinary practice of the three dairy farms that the calves came from was also contacted by phone.
Outcome
Over the past two decades, small numbers of cases (0-6) of polyserositis caused by Mannheimia haemolytica have been diagnosed every year in breeding calves; there were four cases in 2024. There has therefore been no increase in the number of cases identified. In two of the three calves submitted, multiplex PCR determined that the Mh was serotype A2, as also found in polyserositis in veal calves. Further investigations revealed that the infection was contracted in group accommodation. The Mh strains detected exhibited little or no resistance to antibiotics, in contrast to the Mh serotype A2 strains usually isolated from veal calves. The farm that was visited was a regular dairy farm.
Polyserositis pilot among breeding calves
Health of cattle in the Netherlands, fourth quarter of 2024
VETERINARY DISEASES
Implementing Regulation (EU) 2018/1882 of Animal Health Regulation (AHR)
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.
Implementing
Bluetongue (BT)
Bovine genital campylobacteriosis
Bluetongue serotype 3 outbreak in the Netherlands since September 2023 (see §3.2.1).
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 are compulsory for dairy farms but voluntary on beef cattle farms.
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 are compulsory for dairy farms but voluntary on beef cattle farms.
(category A disease)
D, E No infections ever detected.
D, E No infections detected.
(categories B to E)
C, D, E 8,734 infections reported; BTV-12 detected in the Netherlands for the first time.
D, E Campylobacter fetus spp. Veneralis not detected.
C, D, E The status* of 91.2 per cent of dairy farms is ‘BVD-free’ or ‘BVD not suspected’.
The status of 21.0 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 82.6 per cent of dairy farms is ‘IBR-free’ or ‘IBR not suspected’.
The status of 21.4 per cent of all non-dairy farms was 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 found on goat farms with no established relationship to human illness.
From the first quarter of 2023 onwards, this is once again part of the aborter pathology protocol.
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 Four 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 are 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 are compulsory for dairy farms but voluntary on beef cattle farms.
Bacterium. Infections detected occasionally in cattle, mostly in aborted foetuses.
- The status of 98.5 per cent of dairy farms is ‘leptospirosis-free’.
The status of 30.2 per cent of non-dairy farms is ‘leptospirosis-free’.
More animals are arriving with a leptospirosis status lower than ‘free’ compared to the previous quarter.
No new leptospirosis infections.
- No infections detected in cattle presented for necropsy; detected twice in aborted foetuses.
- The bulk milk results of 93.3 per cent of dairy farms are favourable (nationwide programme).
- Detected on four occasions.
Royal GD P.O. Box 9, 7400 AA Deventer
T. +31 (0)88 20 25 575
info@gdanimalhealth.com www.gdanimalhealth.com
VETERINARY DISEASES
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 ovine 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.
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.
- No infections detected.
Table continuation
- No infections confirmed upon necropsy.
- Infections were detected at 46 farms and in seven animals presented for necropsy.
- One infection detected in the aborted foetuses submitted for necropsy.
- Two samples were submitted for investigation; no infections were detected.
